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IP NETWORKING OVERVIEW
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AGENDA
1. Network Basics and OSI Layers
2. LAN Components
3. IP Addressing
4. Switching Concepts 5. Routing Concepts
6. Network Troubleshooting and Overview on
DNS and DHCP
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WHATISA NETWORK
A network can be defined as two or more computers connected together in
such a way that they can share resources.
It is simply a collection of computers or other hardware devices that are
connected together, either physically or logically, using special hardware and
software, to allow them to exchange information and cooperate. Networking
is the term that describes the processes involved in designing, implementing,upgrading, managing and otherwise working with networks and network
technologies.
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WHYNETWORKISREQUIRED
Connectivity and Communication
Data Sharing
Hardware Sharing Internet Access
Internet Access Sharing
Data Security and Management
Performance Enhancement and Balancing
Entertainment
In general, the purpose of a network is to share resources.
A resource may be: A file
A folder
A printer
A disk drive
Or just about anything else that exists on a computer.
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NETWORK CLASSIFICATIONS
Local Area Networks (LANs):
A local area network (LAN) is a computer network covering a smallgeographic area, like a home, office, or group of buildings
Wide Area Networks (WANs):
Wide Area Network (WAN) is a computer network that covers a broad area(i.e., any network whose communications links cross metropolitan, regional,or national boundaries). Or, less formally, a network that uses routers andpublic communications links
The largest and most well-known example of a WAN is the Internet.
WANs are used to connect LANs and other types of networks together, sothat users and computers in one location can communicate with users andcomputers in other locations
Metropolitan Area Network (MAN):
A metropolitan area network (MAN) is a network that interconnects users with
computer resources in a geographic area or region larger than that covered
by even a large local area network (LAN) but smaller than the area coveredby a wide area network (WAN). The term is applied to the interconnection of
networks in a city into a single larger network (which may then also offer
efficient connection to a wide area network). It is also used to mean the
interconnection of several local area networks by bridging them with
backbone lines. The latter usage is also sometimes referred to as a campus
network.
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OSI LAYERS
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OSI LAYERS
Application Layer
This layer provides network services to application processes (such as electronic
mail, file transfer and terminal emulation) Presentation Layer
This layer provides independence from differences in data representation (e.g.,
encryption) by translating from application to network format, and vice versa. The
presentation layer works to transform data into the form that the application layer
can accept. This layer formats and encrypts data to be sent across a network,
providing freedom from compatibility problems. It is sometimes called the syntaxlayer.
Session Layer
This layer establishes, manages and terminates connections between applications.
The session layer sets up, coordinates, and terminates conversations, exchanges,
and dialogues between the applications at each end. It deals with session and
connection coordination.
Transport Layer
This layer provides transparent transfer of data between end systems, orhosts,
and is responsible for end-to-end error recovery and flow control. It ensures
complete data transfer.
http://www.webopedia.com/quick_ref/TERM/H/host.htmlhttp://www.webopedia.com/quick_ref/TERM/F/flow_control.htmlhttp://www.webopedia.com/quick_ref/TERM/F/flow_control.htmlhttp://www.webopedia.com/quick_ref/TERM/H/host.html7/27/2019 IP Networking Overview_Issue 1.0
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OSI LAYERS
Network Layer
This layer provides switching and routing technologies, creating logical paths,
known as virtual circuits, for transmitting data from node to node. Routing andforwarding are functions of this layer, as well as addressing, internetworking, error
handling, congestion control and packet sequencing.
Data Link Layer
At this layer, data packets are encoded and decoded into bits. It furnishes
transmission protocol knowledge and management and handles errors in the
physical layer, flow control and frame synchronization. The data link layer is
divided into two sub layers: The Media Access Control (MAC) layer and the Logical
Link Control (LLC) layer. The MAC sub layer controls how a computer on the
network gains access to the data and permission to transmit it. The LLC layer
controls frame synchronization, flow control and error checking.
Physical Layer:
This layer conveys the bit stream - electrical impulse, light or radio signal --
through the network at the electrical and mechanical level. It provides the
hardware means of sending and receiving data on a carrier, including defining
cables, cards and physical aspects. Fast Ethernet, RS232, and ATM are protocols
with physical layer components
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PHYSICAL LAN COMPONENTS
LAN consists of two major components :
1. Passive (dead) Components : Cable UTP (Un-shielded Twisted Pair)
CAT 5 supports upto 100 Mbps
CAT 5e supports upto 1000 Mbps (1 Gbps)
CAT 6
Supports 1,000 Mbps (1 Gbps)CAT 7 Supports upto 10,000 Mbps (10 Gigabits per second)
Connectors Patch Panel, Information Outlet, RJ-45 etc.
Patch cord for connecting the device to the I/O box.
2. Active Components :(require power supply, generates electric signals, capable of amplification)
Hub : 10/100 Mbps.
Switch : 10/100 Mbps or 10/100/1000 Mbps (GBIC)
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PASSIVE COMPONENTS
Patch cord : A small factory made flexible cable having
RJ-45 connectors at both the ends. Used to connect PCsNetwork card to the I/O or Patch-panel and switch-port.
Patch-Panel : It has RJ-45 interface at one end and open-pins at the other end. Used to terminated the horizontal-run cable at
the switch-end / Network rack/IT room.
Uplink : Generally An UTP/OF cable which runs betweenfloors/switches to connected two floors/switches.
Horizontal Run : A long UTP (Unshielded-Twisted-Pair)cable (Cat5/Cat5e/Cat6) running between I/O and Patch-panel.
I/O : Information-Outlet has RJ-45 interface at one end andopen-pins at the other end. This is used to terminated the
horizontal-run at the users end.
http://images.google.co.in/imgres?imgurl=http://www.fastlinkcabling.com/SPP1.jpg&imgrefurl=http://www.fastlinkcabling.com/&h=1200&w=1600&sz=326&hl=en&start=19&tbnid=93BWqNgQTpI2WM:&tbnh=113&tbnw=150&prev=/images?q=network+switches&gbv=2&svnum=10&hl=enhttp://images.google.co.in/imgres?imgurl=http://www.fastlinkcabling.com/SPP1.jpg&imgrefurl=http://www.fastlinkcabling.com/&h=1200&w=1600&sz=326&hl=en&start=19&tbnid=93BWqNgQTpI2WM:&tbnh=113&tbnw=150&prev=/images?q=network+switches&gbv=2&svnum=10&hl=en7/27/2019 IP Networking Overview_Issue 1.0
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TYPESOF COPPER CABLES
StraightThrough cable : The Straight-through cable hasidentical ends => ( used as a patch cord to connect different type of devices
e.g. PC to Switch).
Cross-Over cable : A cross-over cable has different ends. The Rxand Tx pairs are reversed between the ends. (Used to connect two Ethernet
devices without a switch or for connecting two switches i.e. similar devices).
Rollover cable : The rollover cable is used to connect a computer'sserial port to the console port of a router or managed switch (with a dongle). It
is wired with the to ends completely the reverse of each other.
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DIFFERENCEBETWEEN HUBAND SWITCH
HubShared Device
10 Mbps or 100 Mbps
All ports share the bandwidth
8 / 12 /16 / 24 Ports
Forwards frames to all the ports
(works on Broadcasting model)
Single collision domain
Supports half-duplex
Switch
Bridging Device
10 / 100 / 1000 Mbps
Each port has dedicated bandwidth
8 / 16 / 24 / 48 Ports & Modular
Forwards frames to the specific ports
(based on MAC address Table)
Multiple collision domain (i.e. Switches
break-up collision domain)
Supports half- as-well-as full-duplex
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INTRODUCTIONTO IP ADDRESSING
The initial host-to-host communications protocol introduced in the ARPANET
was called the Network Control Protocol (NCP). Over time, however, NCP
proved to be incapable of keeping up with the growing network traffic load. In1974, a new, more robust suite of communications protocols was proposed
and implemented throughout the ARPANET, based upon the Transmission
Control Protocol (TCP) for end-to-end network communication. But it seemed
like overkill for the intermediate gateways (what we would today call routers)
to needlessly have to deal with an end-to-end protocol so in 1978 a new
design split responsibilities between a pair of protocols; the new InternetProtocol (IP) for routing packets and device-to-device communication (i.e.,
host-to-gateway or gateway-to-gateway) and TCP for reliable, end-to-end
host communication. Since TCP and IP were originally envisioned
functionally as a single protocol, the protocol suite, which actually refers to a
large collection of protocols and applications, is usually referred to simply as
TCP/IP.
An Internet Protocol (IP) address is a numerical label that is assigned to
devices participating in a computer network that uses the Internet Protocol for
communication between its nodes.
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IP ADDRESSING
An IP address is a 32-bit sequence of 1s and 0s.
To make the IP address easier to use, the address is usually written as fourdecimal numbers separated by periods.
This way of writing the address is called the dotted decimal format.
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IPV4 ADDRESSING
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CLASS A, B, C, D, AND E IP ADDRESSES
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RESERVED IP ADDRESSES
Certain host addresses are reserved
and cannot be assigned to devices
on a network.
An IP address that has binary 0s in
all host bit positions is reserved for
the network address.
An IP address that has binary 1s in
all host bit positions is reserved for
the network address.
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PUBLICAND PRIVATE IP ADDRESSES
No two machines that connect to a public network can have the same IPaddress because public IP addresses are global and standardized.
However, private networks that are not connected to the Internet may useany host addresses, as long as each host within the private network isunique.
RFC 1918 sets aside three blocks of IP addresses for private, internal use.
Connecting a network using private addresses to the Internet requirestranslation of the private addresses to public addresses using NetworkAddress Translation (NAT).
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INTRODUCTIONTO SUBNETTING
To create a subnet address, a network administrator borrows bits from the
host field and designates them as the subnet field.
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MAC ADDRESS LAYER 2
Why MAC Addresses ? Recall that TCP/IP and other mainstream networking architectures generally
adopt the OSI model. In this model, network functionality is subdivided intolayers. MAC addresses function at the data link layer (layer 2 in the
OSI model). They allow computers to uniquely identify themselves on a
network at this relatively low level.
What is a MAC address ?
The MAC address is a unique value associated with a network adapter. MACaddresses are also known as hardware addresses or physical addresses.
They uniquely identify an adapter on a LAN.
MAC addresses are 12-digit hexadecimal numbers (48 bits in length). By
convention, MAC addresses are usually written in one of the following two
formats. The first half of a MAC address contains the ID number of the adapter
manufacturer. These IDs are regulated by an Internet standards body (see
sidebar). The second half of a MAC address represents the serial number
assigned to the adapter by the manufacturer
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ADDRESS RESOLUTION PROTOCOL (ARP)
Each device on a network maintains its own ARP table.
A device that requires an IP and MAC address pair broadcasts an ARPrequest.
If one of the local devices matches the IP address of the request, it sendsback an ARP reply that contains its IP-MAC pair.
If the request is for a different IP network, a router performs a proxy ARP
The router sends an ARP response with the MAC address of the interface onwhich the request was received, to the requesting host.
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WAN
A wide area network(WAN)is a computer network covering multiple distance
areas, which may spread across the entire world. WANs often connect
multiple smaller networks, such as local area networks (LANs) or metro areanetworks (MANs). The world's most popular WAN is the Internet. Some
segments of the Internet are also WANs in themselves. A wide area network
may be privately owned or rented from service providers, but the term usually
connotes the inclusion of public (shared user) networks.
A virtual private network (VPN) is often used by organizations for their private
and secured communications. VPN uses encryption and other techniques to
make it appear that the organisation has a dedicated network while making
use of the shared infrastructure of the WAN.
WANs generally utilize different networking technologies and equipment thando LANs. Key technologies often found in WANs include SONET, Frame
Relay, X.25, ATM, and PPP
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ROUTEDAND ROUTING PROTOCOLS
A routing protocol sends and receives routing information packets to and from
other routers.
A routed protocol can be routed by a router, which means that it can be
forwarded from one router to another.
A routed protocol contains the data elements required for a packet to be sent
outside of its host network or network segment. In other words, a routedprotocol can be routed.
Protocols used to communicate routing information between routers within an
autonomous system are Interior Gateway Protocols (IGP), which are routing
protocols, but not routed protocols.
Examples of routed protocols are IP and IPX, and examples of routing
protocols are RIP and IGRP.
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SWITCHING
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ETHERNET/802.3 LAN DEVELOPMENT
Distance limitations
Ethernet is fundamentally a shared technology where all users on a given LANsegment compete for the same available bandwidth.
This situation is analogous to a number of cars all trying to access a one-laneroad at the same time.
Because the road has only one lane, only one car can access it at a time.
The introduction of hubs into a network resulted in more users competing forthe same bandwidth.
Collisions are a by-product of Ethernet networks.
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BRIDGES
A bridge is a Layer 2 device used to divide, or segment, a network.
A bridge is capable of collecting and selectively passing data frames between
two network segments.
Bridges do this by learning the MAC address of all devices on each connected
segment. Using this information, the bridge builds a bridging table andforwards or blocks traffic based on that table.
This results in smaller collision domains and greater network efficiency.
Bridges do NOT restrict broadcast traffic.
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SWITCHES
Switches create a virtual circuit between two connected devices, establishing a
dedicated communication path between two devices.
Switches on the network provide microsegmentation.
This allows maximum utilization of the available bandwidth.
A switch is also able to facilitate multiple, simultaneous virtual circuit
connections.
Broadcast frames to all connected devices on the network.
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ELEMENTSOF ETHERNET/802.3 NETWORKS
Broadcast data frame delivery of Ethernet/802.3
The carrier sense multiple access/collision detect (CSMA/CD) method allowsonly one station to transmit at a time.
Multimedia applications with higher bandwidth demand such as video and theInternet, coupled with the broadcast nature of Ethernet, can create networkcongestion.
Normal latency as the frames travel across the layers
Extending the distances and increasing latency of the Ethernet/802.3 LANs byusing Layer 1 repeaters.
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HALF-DUPLEX
Originally Ethernet was a half-duplex technology.
Using half-duplex, a host could either transmit or receive at one time, but not both.
If the network is already in use, the transmission is delayed.
When a collision occurs, the host that first detects the collision will send out a jam signalto the other hosts.
Upon receiving the jam signal, each host will stop sending data, then wait for a randomperiod of time before attempting to retransmit.
The back-off algorithm generates this random delay.
As more hosts are added to the network and begin transmitting, collisions are more likely
to occur.
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FULL-DUPLEXTRANSMITTING
Full-duplex Ethernet allows the transmission of a packet and the reception of adifferent packet at the same time.
To transmit and receive simultaneously, a dedicated switch port is required foreach node.
The full-duplex Ethernet switch takes advantage of the two pairs of wires in thecable by creating a direct connection between the transmit (TX) at one end ofthe circuit and the receive (RX) at the other end.
Ethernet usually can only use 50%-60% of the available 10 Mbps of bandwidthbecause of collisions and latency.
Full-duplex Ethernet offers 100% of the bandwidth in both directions.
This produces a potential 20 Mbps throughput, which results from 10 Mbps TX
and 10 Mbps RX.
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LAN SEGMENTATION
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Two common types of access methods for LANs include
Non-Deterministic: Contention methods (Ethernet, IEEE 802.3)
Only one signal can be on a network segment at one time.
Collisions are a normal occurrence on an Ethernet/802.3 LAN
Deterministic: Token Passing (Token Ring)
ACCESS METHODS
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CSMA/CD
CSMA/CD (Carrier Sense Multiple Access with Collision
Detection) Common contention method used with Ethernet and IEEE 802.3
Let everyone have access whenever they want and we will work it out
somehow.
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CSMA/CD (Carrier Sense Multiple Access with Collision Detection)
Listens to the networks shared media to see if any other users on on the
line by trying to sense a neutral electrical signal or carrier. If no transmission is sensed, then multiple access allows anyone onto the
media without any further permission required.
If two PCs detect a neutral signal and access the shared media at the exactsame time, a collision occurs and is detected.
The PCs sense the collision by being unable to deliver the entire frame
(coming soon) onto the network. (This is why there are minimum framelengths along with cable distance and speed limitations. This includes the 5-4-3 rule.)
When a collision occurs, a jamming signal is sent out by the first PC to detectthe collision.
Using either a priority or random backoff scheme, the PCs wait certain
amount of time before retransmitting. If collisions continue to occur, the PCs random interval is doubled, lessening
the chances of a collision.
CSMA/CD AND COLLISIONS
CSMA/CD C
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And as we said,
When information (frame) is transmitted, every PC/NIC on the shared mediacopies part of the transmitted frame to see if the destination address matches
the address of the NIC.
If there is a match, the rest of the frame is copied
If there is NOT a match the rest of the frame is ignored.
1111 2222 3333 nnnn Abbreviated
MAC
Addresses
11113333
NopeNope
Hey, thats
me!
Notice the
location of
the DA!
CSMA/CD AND COLLISIONS
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SENDINGANDRECEIVING ETHERNETFRAMESVIAAHUB
So, what does a hub do when it
receives information?
Remember, a hub is nothingmore than a multiport repeater.
1111 2222
3333 4444
5555
?
11113333
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SENDINGANDRECEIVING ETHERNETFRAMESVIAAHUB
Hub or
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SENDINGANDRECEIVING ETHERNETFRAMESVIAAHUB
The hub will flood it out all portsexcept for the incoming port.
Hub is a layer 1 device.
A hub does NOT look at layer 2addresses, so it is fast intransmitting data.
Disadvantage with hubs: A hubor series of hubs is a singlecollision domain.
A collision will occur if any two ormore devices transmit at thesame time within the collisiondomain.
1111 2222
3333 4444
5555
11113333
Nope
Nope
Nope
For me!
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SENDINGANDRECEIVING ETHERNETFRAMESVIAAHUB
Another disadvantage with hubsis that is take up unnecessarybandwidth on other links.
1111 2222
3333 4444
5555
11112222
Nope Nope
Nope
For me!
Wasted
bandwidth
S E
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SENDINGANDRECEIVING ETHERNETFRAMESVIAASWITCH
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SENDINGANDRECEIVING ETHERNETFRAMESVIAASWITCH
Source Address Table
Port Source MAC Add. Port Source MAC Add.
Switches are also known aslearning bridges orlearningswitches.
A switch has a source address
table in cache (RAM) where itstores source MAC address after itlearns about them.
A switch receives an Ethernetframe it searches the sourceaddress table for the Destination
MAC address. If it finds a match, it filters the
frame by only sending it out thatport.
If there is not a match iffloods itout all ports.
switch
1111
2222
3333
4444
AbbreviatedMACaddresses
11113333
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NO DESTINATION ADDRESSINTABLE, FLOOD
Source Address Table
Port Source MAC Add. Port Source MAC Add.
1 1111
How does it learn source MAC
addresses?
First, the switch will see if the SA
(1111) is in its table.
If it is, it resets the timer (more in a
moment).
If it is NOT in the table it adds it,
with the port number.
Next, in our scenario, the switch
will flood the frame out all otherports, because the DA is not in the
source address table.
switch
1111
2222
3333
4444
AbbreviatedMACaddresses
11113333
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DESTINATION ADDRESSINTABLE, FILTER
Source Address Table
Port Source MAC Add. Port Source MAC Add.
1 1111 6 3333
Most communications involvesome sort of client-serverrelationship or exchange ofinformation. (You will understand
this more as you learn aboutTCP/IP.)
Now 3333 sends data back to1111.
The switch sees if it has the SAstored.
It does NOT so it adds it. (This willhelp next time 1111 sends to3333.)
Next, it checks the DA and in ourcase it can filterthe frame, bysending it only out port 1.
switch
1111
2222
3333
4444
AbbreviatedMACaddresses
33331111
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DESTINATION ADDRESSINTABLE, FILTER
Source Address Table
Port Source MAC Add. Port Source MAC Add.
1 1111 6 3333
Now, because both MACaddresses are in the switchs table,any information exchangedbetween 1111 and 3333 can besent (filtered) out the appropriateport.
What happens when two devicessend to same destination?
What if this was a hub?
Where is (are) the collision
domain(s) in this example?
switch
1111
2222
3333
4444
AbbreviatedMACaddresses
11113333
33331111
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NO COLLISIONSIN SWITCH, BUFFERING
Source Address Table
Port Source MAC Add. Port Source MAC Add.
1 1111 6 3333
9 4444
Unlike a hub, a collision does NOToccur, which would cause the two
PCs to have to retransmit the
frames.
Instead the switch buffers the
frames and sends them out port #6
one at a time.
The sending PCs have no idea that
their was another PC wanting to
send to the same destination.
switch
1111
2222
3333
4444
AbbreviatedMACaddresses
11113333
44443333
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COLLISION DOMAINS
Source Address Table
Port Source MAC Add. Port Source MAC Add.
1 1111 6 3333
9 4444
When there is only one device on aswitch port, the collision domain is
only between the PC and the
switch. (Cisco curriculum is
inaccurate on this point.)
With a full-duplex PC and switch
port, there will be no collision,
since the devices and the medium
can send and receive at the same
time.
switch
1111
2222
3333
4444
AbbreviatedMACaddresses
11113333
44443333
Collision Domains
WHAT HAPPENS HERE?
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WHATHAPPENSHERE?
33331111
3333
1111
Source Address Table
Port Source MAC Add. Port Source MAC Add.
1 1111 6 3333
1 2222 1 5555
2222 5555
Collision Domain
LAN SEGMENTATION WITH ROUTERS
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LAN SEGMENTATIONWITHROUTERS
Routers provide segmentation of networks, adding a latency factor of 20% to30% over a switched network.
This increased latency is because a router operates at the network layer anduses the IP address to determine the best path to the destination node.
Bridges and switches provide segmentation within a single network orsubnetwork.
Routers provide connectivity between networks and subnetworks.
Routers also do not forward broadcasts while switches and bridges mustforward broadcast frames.
HO S C S SS S
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HOWSWITCHESLEARNADDRESSES
Bridges and switches learn in the following ways:
Reading the source MAC address of each received frame or datagram
Recording the port on which the MAC address was received.
The bridge or switch learns which addresses belong to the devices connectedto each port.
The learned addresses and associated port or interface are stored in theaddressing table.
The bridge examines the destination address of all received frames.
The bridge then scans the address table searching for the destination address.
FILTER OR FLOOD (SWITCH)
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FILTEROR FLOOD (SWITCH)
If a switch has the frames destination address in its CAM table (or SourceAddress Table) it will only send the frame out the appropriate port.
If a switch does not have the frames destination MAC address in its CAMtable, it floods (sends) it out all ports except for the incoming port (the port thatthe frame came in on) known as an Unknown Unicast, or if the destinationMAC address is a broadcast.
Note: A CAM table may contain multiple entries per port, if a hub or a switch isattached to that port.
Most Ethernet bridges can filter broadcast and multicast frames.
FILTER OR FLOOD (SWITCH)
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FILTEROR FLOOD (SWITCH)
Switches flood frames that are:
Unknown unicasts
Layer 2 broadcasts
Multicasts (unless running multicast snooping or IGMP)
Multicast are special layer 2 and layer 3 addresses that are sent to
devices that belong to that group.
WHY SEGMENT LANS? (LAYER 2 SEGMENTS)
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WHYSEGMENT LANS? (LAYER 2 SEGMENTS)
switch
1111
2222
3333
4444
AbbreviatedMAC
addresses
A switch employs
microsegmentation to reduce the
collision domain on a LAN.
The switch does this by creating
dedicated network segments, or
point-to-point connections.
Collision Domains
SWITCHES AND BROADCAST DOMAINS
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SWITCHESANDBROADCASTDOMAINS
These are logical notphysical representationsof what happens tothese frames.
Switches flood frames that are:
Unknown unicasts
Layer 2 broadcasts
Multicasts (unless running multicast snooping or IGMP)
Multicast are special layer 2 and layer 3 addresses that are sent to
devices that belong to that group.
SWITCHES AND BROADCAST DOMAINS
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SWITCHESANDBROADCASTDOMAINS
When a device wants to send out a Layer 2 broadcast, the destination MACaddress in the frame is set to all ones.
A MAC address of all ones is FF:FF:FF:FF:FF:FF in hexadecimal.
By setting the destination to this value, all the devices will accept and processthe broadcasted frame.
SWITCHES AND BROADCAST DOMAINS
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SWITCHESANDBROADCASTDOMAINS
COMMUNICATION BETWEEN SWITCHES AND WORKSTATION
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COMMUNICATIONBETWEENSWITCHESANDWORKSTATION
INTRODUCTION TO VLANS
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INTRODUCTIONTO VLANS
VLANS
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VLANS
VLANs logically segment switched networks based on an organization's
functions, project teams, or applications as opposed to a physical or
geographical basis.
BROADCAST DOMAINS
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BROADCAST DOMAINS
EXAMPLE WITH 3 BROADCAST DOMAINS, 3 VLANS
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EXAMPLEWITH 3 BROADCAST DOMAINS, 3 VLANS
VLAN CONFIGURATION
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BENEFITSOF VLANS
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Easily move workstations on the LAN
Easily add workstations to the LAN
Easily change the LAN configuration
Easily control network traffic
Improve security
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VLAN TYPES
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INTER-SWITCH LINK
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OBJECTIVES
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Trunking
VTP
Inter-VLAN routing
HISTORYOF TRUNKING
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TRUNKING CONCEPTS
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FRAME FILTERING
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FRAME TAGGING
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INTER-SWITCH LINK PROTOCOL
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VLANSAND TRUNKING
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FRAME TAGGINGAND ENCAPSULATION METHODS
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VTP BENEFITS
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VTP CONCEPTS
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The role of VTP is to maintain VLAN configuration consistency across
a common network administration domain.
VTP MODE COMPARISON
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VTP OPERATION
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VTP IMPLEMENTATION
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There are two types of VTP advertisements:
Requests from clients that want information at bootup Responses from servers
There are three types of VTP messages:
Advertisement requests
Summary advertisements
Subset advertisements
VTP BASIC CONFIGURATION STEPS
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1. Determine the version number
2. Choose the domain
3. Choose the VTP mode
4. Password protect the domain
INTER-VLAN ROUTING
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INTER-VLAN ISSUESAND SOLUTIONS
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Two of the most common issues that arise in a multiple-VLAN environment are
\as follows:
The need for end-user devices to reach nonlocal hosts
The need for hosts on different VLANs to communicate
ROUTERONA STICK
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PHYSICALAND LOGICAL INTERFACES
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DIVIDING PHYSICAL INTERFACESINTO SUBINTERFACES
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OBJECTIVES
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Redundant topologies
Spanning Tree Protocol
REDUNDANCY
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Redundant networking topologies are designed to ensure that networks
continue to function in the presence of single points of failure.
REDUNDANT TOPOLOGIES
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A goal of redundant topologies is to eliminate network outages caused by a
single point of failure.
All networks need redundancy for enhanced reliability.
SIMPLE REDUNDANT SWITCHED TOPOLOGY
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BROADCAST STORM
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MULTIPLE FRAME TRANSMISSIONS
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MEDIA ACCESS CONTROL DATABASE INSTABILITY
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In a redundant switched network, it is possible for switches to learn the
wrong information. A switch can learn that a MAC address is on a port
when it is not.
USING BRIDGING LOOPSFOR REDUNDANCY
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SPANNING-TREE PROTOCOL
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SPANNING TREE LINK COSTS
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A SPANNING TREE
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SPANNING-TREE OPERATION
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One root bridge per network.
One root port per nonroot
bridge.
One designated port per
segment.
Nondesignated ports areunused.
BRIDGE PROTOCOL DATA UNIT
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Bridge protocol data unit
(BPDU)
BRIDGE IDS
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SPANNING-TREE PORT STATES
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SPANNING-TREE RECALCULATION
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A switched internetwork has converged when all the switch and bridge ports
are in either the forwarding or blocked state.
RAPID SPANNING-TREE PROTOCOL
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The standard and protocol introduce the following:
Clarification of port states and roles
Definition of a set of link types that can go to forwarding state rapidly
Allowing switches, in a converged network, to generate their ownBPDUs rather than relaying root bridge BPDUs
RAPID SPANNING-TREE PORT DESIGNATIONS
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The Rapid Spanning Tree Protocol, IEEE 802.1w, will eventually replace
the Spanning Tree Protocol, IEEE 802.1D.
TIMEFOR LAYER 3 REDUNDANCY (HIGH-AVAILABILITY)
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WHYYOUNEED IMPLEMENTING HIGH AVAILABILITY?
http://www.google.co.in/url?sa=i&source=images&cd=&cad=rja&docid=8o6C0sYIHc-qmM&tbnid=2mJdDG8zZjaPaM:&ved=0CAgQjRwwAA&url=http://blogs.villagevoice.com/runninscared/2011/02/magic_johnson_n.php&ei=05n3Uc3zCM2rhQf7lIHoCw&psig=AFQjCNHipXGaTbvlb_KXacQ5ohFnyWXt6g&ust=13752676672777007/27/2019 IP Networking Overview_Issue 1.0
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ROUTER REDUNDACY
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FIRST HOP REDUNDANCY SCHEMES
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Hot Standby Router Protocol (HSRP) Cisco informational RFC 2281 ( March 1998)
Virtual Router Redundancy Protocol (VRRP) IETF Standard RFC 2338 (April 1998)
Gateway Load Balancing Protocol (GLBP) Cisco designed, load sharing, patent pending
HSRP
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A group of routers function as one virtual router by sharing ONE virtual IP
address and ONE virtual MAC address.
One (Active) router performs packet forwarding for local hosts
The rest of the routers provide hot standby in case the active routerfails
Standby routers stay idle as far as packet forwarding from the client side isconcerned
FIRST HOP REDUNDANCYWITH HSRP
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Gateway routers
CL1 CL2 CL3
HSRP ACTIVE HSRP STANDBY HSRP LISTEN
Clients
R1 R2 R3
R1- Active, forwarding traffic; R2, R3 - hot standby, idle
IP: 10.0.0.254MAC: 0000.0c12.3456
vIP: 10.0.0.10
vMAC: 0000.0c07ac00
IP: 10.0.0.253MAC: 0000.0C78.9abc
vIP:
vMAC:
IP: 10.0.0.252MAC: 0000.0cde.f123
vIP:
vMAC:
IP: 10.0.0.1
MAC: aaaa.aaaa.aa01
GW: 10.0.0.10
ARP: 0000.0c07.ac00
IP: 10.0.0.2
MAC: aaaa.aaaa.aa02
GW: 10.0.0.10
ARP: 0000.0c07.ac00
IP: 10.0.0.3
MAC: aaaa.aaaa.aa03
GW: 10.0.0.10
ARP: 0000.0c07.ac00
VRRP
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Very similar to HSRP
A group of routers function as one virtual router by sharing ONE virtual IPaddress and ONE virtual MAC address
One (master) router performs packet forwarding for local hosts
The rest of the routers act as back up in case the master routerfails
Backup routers stay idle as far as packet forwarding from the client side isconcerned
FIRST HOP REDUNDANCYWITH VRRP
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Gateway routers
CL1 CL2 CL3
VRRP ACTIVE VRRP BACKUP VRRP BACKUP
Clients
R1 R2 R3
R1- Master, forwarding traffic; R2, R3 - backup
IP: 10.0.0.254MAC: 0000.0c12.3456
vIP: 10.0.0.10
vMAC: 0000.5e00.0100
IP: 10.0.0.253MAC: 0000.0C78.9abc
vIP:
vMAC:
IP: 10.0.0.252MAC: 0000.0cde.f123
vIP:
vMAC:
IP: 10.0.0.1
MAC: aaaa.aaaa.aa01
GW: 10.0.0.10
ARP: 0000.5e00.0100
IP: 10.0.0.2
MAC: aaaa.aaaa.aa02
GW: 10.0.0.10
ARP: 0000.5e00.0100
IP: 10.0.0.3
MAC: aaaa.aaaa.aa03
GW: 10.0.0.10
ARP: 0000.5e00.0100
GLBP DEFINED
A f t f ti i t l t b h i ONE i t l IP
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A group of routers function as one virtual router by sharing ONE virtual IPaddress but using Multiple virtual MAC addresses for traffic forwarding
Provides uplink load-balancing as well as first hop fail-over
IP Leadership feature
GLBP REQUIREMENTS
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Allow traffic from a single common subnet to go through multiple redundantgateways using a single virtual IP address
Provide upstream load-balancing by utilizing the redundant up-linkssimultaneously
Eliminate the need to create multiple vLANs or manually divide clients formultiple gateway IP address assignment
Preserve the same level of first-hop failure recovery capability as provided byHSRP
FIRST HOP REDUNDANCYWITH GLBP
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Gateway routers
CL1 CL2 CL3
GLBP AVG/AVF,SVF GLBP AVF,SVF GLBP AVF,SVF
Clients
R1 R2 R3
R1- AVG; R1, R2, R3 all forward traffic
IP: 10.0.0.254MAC: 0000.0c12.3456
vIP: 10.0.0.10
vMAC: 0007.b400.0101
IP: 10.0.0.253MAC: 0000.0C78.9abc
vIP: 10.0.0.10
vMAC: 0007.b400.0102
IP: 10.0.0.252MAC: 0000.0cde.f123
vIP: 10.0.0.10
vMAC: 0007.b400.0103
IP: 10.0.0.1
MAC: aaaa.aaaa.aa01
GW: 10.0.0.10
ARP: 0007.B400.0101
IP: 10.0.0.2
MAC: aaaa.aaaa.aa02
GW: 10.0.0.10
ARP: 0007.B400.0102
IP: 10.0.0.3
MAC: aaaa.aaaa.aa03
GW: 10.0.0.10
ARP: 0007.B400.0103
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Routing
ROUTING TYPES
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Hoboken#show ip route
Codes: C - connected, S - static,
S 172.16.1.0/24 [1/0] is directly connected, Serial0
C 192.168.2.0/24 is directly connected, Ethernet0
The cost for all static routes is 0
The default administrative distance for
static routes is 1
ADMINISTRATIVE DISTANCE
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Administrative Distance is the trustworthiness of the routing information. Lower the administrative distance the more trustworthy the information. If the router hears about a route to the same network from more than one
source it will use the administrative distance to decide which route to put inthe routing table.
STATIC ROUTING
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172.16.0.0/16 192.168.1.0/24
.1 .1.2 .2
RTA RTB RTC
192.168.2.0/24
.1 .1
10.1.0.0/16
s0 s0 s1s1e0 e0
Configuring static routes
Routers do not need to configure static routes for their own directly connected
networks.
We need to configure static routes for networks this router needs to reach. We will need to configure static routes for the other routers as well, as routing
information about a path from one network to another does not provide routing
information about the reverse, or return path.
Convergence When all the routers in the network (AS) have accurate and
consistent information, so that proper routing and packet forwarding can take
place.
Convergence will not happen until all the routers have complete and accurate
routing information, meaning we must configure static routes on all the routers
before packets will be correctly delivered.
STATIC ROUTING
172.16.0.0/16 192.168.1.0/24192.168.2.0/24 10.1.0.0/16
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.1 .1.2 .2
RTA RTB RTC
.1 .1
s0 s0 s1s1e0 e0
1
2
RTA(config)#ip route 192.168.1.0 255.255.255.0 172.16.0.2
RTA#show ip route
Codes: C - connected, S - static,
C 172.16.0.0/16 is directly connected, Serial0S 192.168.1.0/24 [1/0] via 172.16.0.2
C 192.168.2.0/24 is directly connected, Ethernet0
Recursive Lookup The router knows it can get to 192.168.1.0/24 network by forwarding the packets
to the router at the ip address of 172.16.0.2 How does the router know how to get to the ip address 172.16.0.2?
It does a recursive lookup first (1) by looking up the 192.168.1.0/24 network and
finding it needs to forward the packet to 172.16.0.2 the router then (2) looks up
the 172.16.0.0 network and sees it can forward it out the interface Serial 0.
DYNAMIC ROUTING ROUTING PROTOCOLS
The goal of a routing protocol is to build and maintain the routing table
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The goal of a routing protocol is to build and maintain the routing table.
This table contains the learned networks and associated ports for those
networks.
Routers use routing protocols to manage information received from other
routers, information learned from the configuration of its own interfaces, along
with manually configured routes.
TYPESOF ROUTING PROTOCOLS
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Distance Vector: RIP, IGRP, EIGRP Link State: OSPF, IS-IS Path Vector: BGP Note: IGRP and EIGRP are Cisco
Proprietary
RIP
Routing Information Protocol (RIP) was originally
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Routing Information Protocol (RIP) was originallyspecified in RFC 1058.
It is a distance vectorrouting protocol.
Hop count is used as the metric for path selection.
If the hop count is greater than 15, the packet is discarded.
Routing updates are broadcast every 30 seconds, by default.
IGRP
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IGRP is a distance vector routing protocol developed by Cisco. IGRP sends routing updates at 90 second intervals, advertising
networks for a particular autonomous system. Key design characteristics of IGRP are a follows:
o The versatility to automatically handle indefinite, complextopologies
o The flexibility needed to segment with different bandwidth anddelay characteristics
o Scalability for functioning in very large networks
IGRP
By default the IGRP routing protocol uses bandwidth and delay as metrics
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By default, the IGRP routing protocol uses bandwidth and delay as metrics.
Additionally, IGRP can be configured to use a combination of variables todetermine a composite metric.
Those variables include: Bandwidth
Delay
Load
Reliability
IGRP has an administrative distance of100, more trustworthy than RIP at120.
This means a Cisco router will prefer an IGRP learned route over a RIP
learned route to the same network.
IGRP TIMERS
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All timers begin at the same time. Update timer = 90 seconds Invalid timer = 270 seconds Holddown timer = 280 seconds Flush timer = 630 seconds
Today, IGRP is showing its age, it lacks support for variablelength subnet masks (VLSM).
Enhanced IGRP (EIGRP) supports VLSM.
EIGRP CONCEPTS
Every EIGRP router maintains a topology table for each configured network
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Every EIGRP router maintains a topology table for each configured network
protocol.
All learned routes to a destination are maintained in the topology table.
Neighbor discovery and recovery Reliable Transport Protocol
DUAL finite-state machine algorithm
Protocol-dependent modules
By forming adjacencies, EIGRP routers:
Dynamically learn of new routes that join their network
Identify routers that become either unreachable or inoperable
Rediscover routers that had previously been unreachable
USING EIGRP WITH IGRP
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EIGRP DATA STRUCTURES
The five EIGRP packet types are as follows:
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The five EIGRP packet types are as follows: Hello (used to discover, verify, and rediscover neighbor routers)
Acknowledgment
Update
Query
Reply
EIGRP SUCCESSORSAND FEASIBLE SUCCESSORS
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FEASIBLE SUCCESSOR ROUTE SELECTION RULES
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CONFIGURING EIGRP
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EIGRP AUTOMATICALLY SUMMARIZES BASEDON CLASS
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ROUTE SELECTION
If a link goes down, DUAL looks for an alternative route path, or feasible
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successor, in the topology table.
If a feasible successor is not found, the route is flagged as Active, orunusable at present.
Query packets are sent to neighboring routers requesting topologyinformation.
DUAL uses this information to recalculate successor and feasible successorroutes to the destination.
OSPF
Open ShortestPath First
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Path First Link State or SPF technology Developed by the IETFs OSPF working group (RFC 1247) Designed for TCP/IP Fast Convergence Variable length netmasks Non-contiguous subnets No need for periodic updates Route authentication
OSPF is defined in RFC2328
LINK-STATE ROUTING
Neighbor discovery
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Construct a Link State Packet (LSP)
Distribute the LSP
Link State Announcement LSA
Route calculation
If a link fails
Flood new LSPs
All routers recalculate their routing tables
OSPF AREAS
Group of contiguous nodes/networks
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Per area topology DB
Invisible outside the area
Reduces routing traffic Backbone Area is contiguous
All others areas must connect to the backbone
Virtual Links
Area 1Area 4
Area 0
Backbone Area
Area 2 Area 3
ROUTER CLASSIFICATIONIN OSPF
Internal Router (IR)
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Area Border Router (ABR)
Backbone Router (BR)
Autonomous System Border Router (ASBR)
Area 0
Area 2 Area 3
IR
ABR/BR
To another AS
ASBR
OSPF ROUTE TYPES
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Intra-Area Route
All routes within an area
Inter-Area Route Routes announced from area to
another by an ABR
External Route Routes imported into OSPF from
another protocol or Static routes
Area 0Area 2 Area 3
ABR
To Another AS
ASBR
ROUTE SUMMARIZATION
Prefix or all subnets
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Prefix or all networks
Area range command
Routes can be summarized only in
ABRs
ASBRs
1.A 1.B 1.C
FDDI
Dual Ring
R1 (ABR)
R2
Network
1
Next Hop
R1
Network
1.A1.B
1.C
Next Hop
R1R1
R1
With
Summarization
Without
Summarization
Backbone
Area 0
Area 1
OSPFS METRICIS COST (BANDWIDTH)
Cisco: Cost = Bandwidth
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Cisco uses a default cost of108/bandwidth
Default bandwidth of the interface (bandwidth command) 108(100,000,000)as the reference bandwid th: This is used so that the
faster links (higher bandwidth) have lower costs.
Routing metrics, lower the cost the better the route.
I.e. RIP: 3 hops is better than 10 hops
Extra: The reference bandwidth can be modified to accommodate
networks with links faster than 100,000,000 bps (100 Mbps). See ospf
auto-cost reference-bandwidth command.
Cost of a route is the cumulative costs of the outgoing interfaces from this
router to the network.
OSPF PACKETTYPES
Share a common protocol header Routing protocol packets are sent with a TOS of 0
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Routing protocol packets are sent with a TOS of 0 Five types of OSPF routing protocol packets
Hello packet type 1 DB Description packet type 2 Link-state request packet type 3 Link-state update packet type 4 Link-state Acknowledgment packet type 5
OSPF LSA TYPES
OSPF has 11 types of LSAs out of which 7 types are used in normal
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scenarios
OSPF ADJACENCYSTATES
1. Establishing router adjacencies
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Down State No Hello received
Init StateHello received, but not with this routers Router ID
Hi, my name is Carlos. Hi, my name is Maria.
Two-way StateHello received, and with this routers Router ID
Hi, Maria, my name is Carlos. Hi, Carlos, my name is Maria.
2. Electing DR and BDR Multi-access (broadcast) segments only
ExStart State with DR and BDR
Two-way State with all other routers
3. Discovering Routes
ExStart State
Exchange State
Loading StateFull State
4. Calculating the Routing Table
5. Maintaining the LSDB and Routing Table
OSPF STUB AREAS
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A stub area has only one entry and exit point.
Topology changes in other areas do not affect stub areas. The ABR is
still the only way out.
STUBVS. TOTALLY STUB
Similarities
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ABR does not advertise Type 4 or 5 LSAs into the area
There should be no OE1 or OE2 routes in the area
ABR advertises a default route to the internal routers
Neither area can have an ASBR in it
Neither area can be the backbone
Differences
Totally stub does not advertise Type 3 LSAs either
Stub routing table: O,O IA, and default route Totally stub routing table: O and default route
Stub Area
R1(config-router)#area 1 stub
R2(config-router)#area 1 stub
Command must be entered on all routers in the area
Totally Stubby Area
R1(config-router)#area 1 stub no-summary
R2(config-router)#area 1 stub
ABR is configured with stub no-summary
Internal routers are configured with stub
NSSA
Many service providers have OSPF areas that have only one exit point, but
th t i ASBR
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the areas contain an ASBR
Solution: Not-So-Stubby Areas (NSSAs)
The ASBR originates a Type 7 LSA
The ABR converts from Type 7 to Type 5
Not-So-Stubby Area
R1(config-router)#area 1 nssa
R2(config-router)#area 1 nssaR2(config-router)#redistribute static
Command must be entered on all routers in the area
ASBR must be configured to inject non-OSPF routes
Totally Not-So-Stubby Area
R1(config-router)#area 1 nssa no-summary
R2(config-router)#area 1 stub
ABR is configured with nssa no-summary
Internal routers are configured with nssa
BORDER GATEWAY PROTOCOL
General Terms
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IGP (Interior Gateway Protocol) - RIP, IGRP, EIGRP, OSPF = Routingprotocol used to exchange routing information within an autonomous system.
EGP (Exterior Gateway Protocol) - BGP = Routing protocol used to exchange
routing information between autonomous systems.
Autonomous SystemA set of routers under the single technical
administration, using an IGP and common metrics to route packets within the
AS, and using an EGP to route packets to other ASs.
BGP is a path vector routing protocol.
BGP
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BGP is a path vector routing protocol.
BGP uses a list of AS numbers through which a packet must pass to reach adestination.
The function of BGP is to:
Exchange routing information between autonomous systems
Guarantee the selection of a loop free path.
BGP4 is the first version of BGP that supports CIDR and route aggregation.
Common IGPs such as RIP, OSPF, and EIGRP use technical metrics. BGP does not use technical metrics.
BGP makes routing decisions based on network policies, or rules (later)
BGP does not show the details of topologies within each AS.
BGP sees only a tree of autonomous systems.
Cisco routers maintain a separate routing table to hold BGP routes.
BGP
BGP updates are carried using TCP on port 179.
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In contrast, RIP updates use UDP port 520
OSPF, IGRP, EIGRP does not use a Layer 4 protocol
Because BGP requires TCP, IP connectivity must exist between BGP peers.
TCP connections must also be negotiated between them before updates can
be exchanged.
Therefore, BGP inherits those reliable, connection-oriented properties from
TCP.
BGP MESSAGE TYPES
Before establishing a BGP peer connection the two neighbors must perform
the standard TCP three way handshake and open a TCP connection to port
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the standard TCP three-way handshake and open a TCP connection to port
179.
After the TCP session is established, BGP peers exchanges several
messages to open and confirm connection parameters and to send BGP
routing information.
All BGP messages are unicast to the one neighbor over the TCP connection.
There are four BGP message types:
Type 1: OPEN
Type 2: KEEPALIVE Type 3: UPDATE
Type 4: NOTIFICATION
BGP STATES
BGP FSM includes six states:
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Idle Connect
Active
OpenSent
Open Confirm
Established
BGP STATES
IDLE StateBGP l b i i th Idl t t i hi h it f ll i i ti
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BGP always begins in the Idle state, in which it refuses all incoming connections.
It is normally initiated by an administrator or a network event.
When Start event occurs, the BGP process: Initializes all BGP resources
Starts the ConnectRetry timer
Initializes a TCP connection to the neighbor
Listens for a TCP initialization from the neighbor
Changes its state to Connect
CONNECT State If the connection is unsuccessful, the BGP process:
Continues to listen for a connection to be initiated by the neighbor
Resets the ConnectRetry timer
Transitions to the Active state
ACTIVE State In this state, the BGP process is waiting for the TCP connection to be completed.
If the connection is successful, the BGP process:
Clears the ConnectRetry timer
Completes initialization
Sends an Open message to the neighbor
Transitions to the OpenSent state
BGP STATES
Open Sent StateI thi t t O h b t d BGP i iti t h O f
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In this state an Open message has been sent and BGP is waiting to hear an Open message from
its neighbor.
When an Open message is received, all its fields are checked. If errors exist, a Notification message is sent and the state transitions to Idle.
If no errors exist, a Keepalive message is sent and the Keepalive timer is set, the peer is
determined to be internal or external, and state is changed to OpenConfirm.
Open Confirm State In this state, the BGP process waits for a Keepalive orNotification message.
If a Keepalive message is received, the state transitions to Established. If a Notification message is received, or a TCP disconnect is received, the state transitions to Idle.
Established State In this state, the BGP connection is fully established and the peers can exchange Update,
Keepalive messages.
If an Update orKeepalive message is received, the Hold timer is restarted.
If a Notification message is received, the state transitions to Idle.
BGP PATH ATTRIBUTES
Much of the work you will do configuring BGP focuses on path attributes.
E h t h it t f d fi d tt ib t hi h i l d th
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Each route has its own set of defined attributes, which can include path
information, route preference, next-hop, and aggregation information.
Administrators use these values to enforce routing policy.
Based on attribute values, you can configure BGP to filter routing information,
prefer certain paths, or otherwise customize its behavior.
Path attributes come in four different types:
Well-known mandatory
Well-known discretionary
Optional transitive
Optional non-transitive
BGP PATH ATTRIBUTES
Well-known mandatory
An attribute that has to exist in the BGP UPDATE packet
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An attribute that has to exist in the BGP UPDATE packet.
It must be recognized by all BGP implementations.
If a well-known attribute is missing, a notification error will be generated; this ensures that all BGPimplementations agree on a standard set of attributes.
Example: AS_PATH attribute.
Well-known discretionary
An attribute that is recognized by all BGP implementations
But may ormay not be sent in the BGP UPDATE message.
Example: LOCAL_PREF
Optional transitive
An attribute that may or may not be, recognized by all BGP implementations (thus, optional).
Because the attribute is transitive, BGP should accept and advertise the attribute even if it isnt
recognized.
Example: COMMUNITY
Optional non-transitive An attribute that may or may not be, recognized by all BGP implementations.
Whether or not the receiving BGP router recognizes the attribute, it is non-transitive, and should
not be passed along to other BGP peers.
Example: ORIGINATOR_ID
BGP PATH ATTRIBUTES
Attribute Code Type
1-ORIGIN Well-known mandatory
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2-AS_PATH Well-known mandatory
3-NEXT_HOP Well-known mandatory
4-MULTI_EXIT_DISC Optional non-transitive5-LOCAL_PREF Well-known discretionary
6-ATOMIC_AGGREGATE Well-known discretionary
7-AGGREGATOR Well-known discretionary
8-COMMUNITY Optional transitive (Cisco)
9-ORIGINATOR_ID Optional non-transitive (Cisco)
10-Cluster List Optional non-transitive (Cisco)
11-Destination Preference (MCI)
12-Advertiser (Baynet)
13-rcid_path (Baynet)
255-Reserved [md]
Summary of the BGP Path Selection Process
BGP selects only one path as the best path.
When the path is selected, BGP puts the selected path in its routingtable and propagates the path to its neighbors.
BGP CONFIGURATION
To begin configuring a BGP process, issue the following familiar command:
Router(config)#router bgp AS number
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Router(config)#router bgpAS-number
BGP configuration commands appear on the surface to mirror the syntax of
familiar IGP (for example, RIP, OSPF) commands.
Although the syntax is similar, the function of these commands is significantly
different.
Note: Cisco IOS permits only one BGP process to run at a time, thus, a
router cannot belong to more than one AS.
EBGP MULTI HOP
EBGP neighbors must be directly connected in order to establish an EBGP
session
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session.
However, EBGP multihop is a Cisco IOS option allows RTW and RTU to be
logically connected in an EBGP session, despite the fact that RTV does notsupport BGP.
The EBGP multihop option is configured on each peer with the following
command:
Router(config-router)#neighborIP-addressebgp-multihop [hops]
RTW(config)#router bgp 200
RTW(config-router)#neighbor 1.1.1.2 remote-as 300
RTW(config-router)#neighbor 1.1.1.2 ebgp-multihop 2
RTU(config)#router bgp 300RTU(config-router)#neighbor 1.1.1.1 remote-as 200
RTU(config-router)#neighbor 1.1.1.1 ebgp-multihop 2
PATH SELECTION PROCESS
BGP uses the following criteria, in the order presented, to select a path for a
destination:
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destination:
1. If the path specifies a next hop that is inaccessible, drop the update.
2. Prefer the path with the largest weight.
3. If the weights are the same, prefer the path with the largest local preference.
4. If no route was originated, prefer the route that has the shortest AS_path.
6. If all paths have the same AS_path length, prefer the path with the lowest
origin type (where IGP is lower than EGP, and EGP is lower thanIncomplete).
7. If the origin codes are the same, prefer the path with the lowest MED
attribute.
8. If the paths have the same MED, prefer the external path over the internal
path.
MPLS VPN
MPLS - VPN is generally Virtual Private Network in which various customers
are allowed to communicate with each other through a common cloud
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are allowed to communicate with each other through a common cloud.
VRF will be configured for each routing instance / customer.
VRF is VPN Routing and Forwarding.
Each VRF will have a VRF name with CASE-SENSITIVE.
VRF is not operational unless you configure RD.
Each VRF will have unique Route Targets both import and import.
We have all these VRFs to be participated in BGP to propagate routing
information.
MPBGP
In MPLS network, we use MP-BGP
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Normal BGP uses IPv4 header between peers. MP-BGP uses VPNV4.
VPNV4 prepends 64bit header infront of IPV4 IP header packet to make itdifferent from.
To make this enable we need to add the following command in BGP
configuration.
address-family vpnv4 unicast.
The purpose of the VRF is to have the separate routing instance for each
customers. In which the customer can be reached to the destination without
any issues in public network.
ICMP & TRACEROUTE
ICMP (Internet Control Messaging Protocol) is used for IP troubleshooting in Networks.
Uses ICMP message within an IP Packet, Protocol field = 1
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Both are layer 3 protocols. (ICMP is considered as a network layer protocol.)
Does not use TCP or UDP, but may be acted upon by the receiver using TCP or UDP.Format
pingip address (orping for extended ping)
ping 172.30.1.25
ICMP & TRACEROUTE (CONTINUED)
Trace ( Cisco = traceroute, tracert,) is used to trace theprobable path apacket takes between source and destination.
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Probable, because IP is a connectionless protocol, and different packets maytake different paths between the same source and destination networks,although this is not usually the case.
Trace will show the path the packet takes to the destination, but the returnpath may be different.
This is more likely the case in the Internet, and less likely within your ownautonomous system.
Uses ICMP message within an IP Packet Both are layer 3 protocols.
Uses UDP as a the transport layer.
Traceroute uses ping (echo requests)
Traceroute sets the TTL (Time To Live) field in the IP Header, initially to 1
10.0.0.0/8 172.16.0.0/16 192.168.10.0/24
.1 .1 .1.2 .2 .2
RTA RTB RTC RTD
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ADD-ONs
(DNS & DHCP)
DNS CONCEPTS
Domains
Uses a hierarchical name space
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Each domain is represented by a branch of the hierarchy
The top of the hierarchy is called the root; all domains branch from the root
Domains represent the conceptual aspect of the DNS system
Zones
Zones are the embodiment of one or more domains on a system that providename resolution: a DNS Server
Typically there is a one-to-one correspondence between Domains andZones, although a zone can have more than one domain
Zone Types: Master
Slave
Forward
Stub
Delegation
The process by which a parent domain turns over responsibility of a childdomain to a different, unique Zone
THE BASICS
DNS is simple: Ask it a question, it gives you an answer; the trick: how the
answer is obtained
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It was designed as a rudimentary directory (data store is simplistic)
The most common questions and answers (informaion supplied by thisdirectory):
Please translate a name to an IP Address
Please translate an IP address to a name
Please give me the IP Address of a gateway so I can deliver e-mail
THE BASICS
Client-Server architecture
Client is called a resolver
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Client is called a resolver
Client queries a pre-configured (manually or via DCHP) DNS server
The DNS server looks up the query data
In its configuration files
In its cache from prior queries
From other DNS servers
Developed at Berkeley
Hierarchical name space
Static mapping originally; dynamic capabilities added later
Defined in a number of IETF RFCs. Predominantly RFC 1034 and 1035
THE BASICS
DNS is implemented in a piece of software that is called a DNS Server. The
most common implementation of the DNS Server is called BIND (Berkeley
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( y
Internet Name Domain) Server.
BIND is currently maintained by an organization called Internet System
Consortium (ISC). The latest version is BIND 9.3.3 and 8.4.7
BIND incorporates most RFCs; it is the reference implementation for all
DNS servers
NAME SPACE STRUCTURE
. (root)
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org gov uscomedu
ins
ins.com Domain
( )
company
hr
finance
company.us Domain
mfg
THE SERVERS
A DNS Server typically has ultimate responsibility (authority) for a part of the
DNS Name Space hierarchy, on a domain boundary
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Maintains information about Domains in Zones
Zones contain the information that is used by the DNS server to answer
questions asked of it
Questions are called queries
Answers are called responses
SERVERS
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DOMAINSAND ZONES
Domains
Domains represent the conceptual aspect of the DNS system (the
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p p p y (
theoretical representation of the domain name space)
Each domain is represented by a branch of the hierarchy Zones
Zones are the embodiment of one or more domains on a system that
provide name resolution: a DNS Server
Typically there is a one-to-one correspondence between Domains and
Zones, although a zone can have more than one domain Zone Types (more on these later):
Master
Slave
Forward
Stub
DOMAINSAND ZONES
Delegation
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The process by which a parent domain turns over responsibility of a childdomain to a different, unique Zone
Delegation is what makes the distribution of the DNS name space to
autonomous organizations possible
DNS CONCEPTS RESOLUTION
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CACHING
When a DNS server is queried for information, it must always find and go to
the authoritative source
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That authoritative source might be itself (if a Master of a Slave for that Zone)
Any information that a DNS server acquires or learns from other DNSservers are retained in memory; this is called caching
Allows subsequent queries that are identical or related to learned
information reduces or eliminate queries to the authoritative source
The authoritative source will indicate to the asking DNS server how long
information can be retained before refreshing the information from theauthoritative source; this is called Time-To-Live for a DNS response, or TTL
DYNAMIC HOST CONFIGURATION PROTOCOL - DHCP
RFC 2131
Runs over UDP as well
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Runs over UDP as well
Provides automatic configuration of the host connected to network or booted
Provides hosts with initial configuration information upon bootup:
IP address with subnet mask,
default gateway,
IP address of the DNS server .
DHCP (CONT.)
server Aclient
server B
(selected)(not selected)
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determine
configuration
determine
configuration
DHCP discoverDHCP discover
DHCP offerDHCP offer
select configuration
DHCP requestDHCP request
DHCP ack
Initialization completes
graceful shutdownDHCP release
discard lease
using the allocated configuration
(se ected)( ot se ected)
DHCP MESSAGES
DHCPDISCOVER The client broadcasts message in search of available DHCP servers
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The client broadcasts message in search of available DHCP servers.
DHCPOFFER The server response to the client DHCPDISCOVER with offer ofconfiguration parameters .
DHCPREQUEST The client broadcasts to the server, requesting offered parameters from
one server specifically.
Confirms correctness of previously allocated address after, e.g., systemreboot.
Extends the lease on a particular network address.
DHCPRELEASE The client-to-server communication, relinquishing network address and
canceling remaining lease.
DHCPACK The server-to-client communication with configuration parameters,
DHCP MESSAGES (CONT.)
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g p
including committed network address.
DHCPNAK Server to client indicating client's notion of network address is incorrect
(e.g., client has moved to new subnet) or client's lease as expired
DHCPDECLINE The client-to-server communication, indicating that the network address is
already in use. DHCPINFORM
The client-to-server communication, asking for only local configuration
parameters that the client already has externally configured as an
address.
REFERENCES
http://compnetworking.about.com/od/basicnetworkingconcepts/Networking_B
asics_Key_Concepts_in_Computer_Networking.htm
http://compnetworking.about.com/od/basicnetworkingconcepts/Networking_Basics_Key_Concepts_in_Computer_Networking.htmhttp://compnetworking.about.com/od/basicnetworkingconcepts/Networking_Basics_Key_Concepts_in_Computer_Networking.htmhttp://compnetworking.about.com/od/basicnetworkingconcepts/Networking_Basics_Key_Concepts_in_Computer_Networking.htmhttp://compnetworking.about.com/od/basicnetworkingconcepts/Networking_Basics_Key_Concepts_in_Computer_Networking.htmhttp://compnetworking.about.com/od/basicnetworkingconcepts/Networking_Basics_Key_Concepts_in_Computer_Networking.htm7/27/2019 IP Networking Overview_Issue 1.0
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http://www.cse.tkk.fi/fi/opinnot/T-110.1100/1999_Tik-110.250/Kalvot/TKK_2_99/index.htm
http://www.cisco.com/cisco/web/psa/reference.html
https://learningportal.juniper.net/juniper/user_activity_info.aspx?id=769
http://www.routeralley.com/ra/docs/stp.pdf
http://www.ircbeginner.com/ircinfo/Routing_Article.pdf
http://www.cse.tkk.fi/fi/opinnot/T-110.1100/1999_Tik-110.250/Kalvot/TKK_2_99/index.htmhttp://www.cse.tkk.fi/fi/opinnot/T-110.1100/1999_Tik-110.250/Kalvot/TKK_2_99/index.htmhttp://www.cisco.com/cisco/web/psa/reference.htmlhttps://learningportal.juniper.net/juniper/user_activity_info.aspx?id=769http://www.routeralley.com/ra/docs/stp.pdfhttp://www.routeralley.com/ra/docs/stp.pdfhttp://www.routeralley.com/ra/docs/stp.pdfhttps://learningportal.juniper.net/juniper/user_activity_info.aspx?id=769https://learningportal.juniper.net/juniper/user_activity_info.aspx?id=769https://learningportal.juniper.net/juniper/user_activity_info.aspx?id=769https://learningportal.juniper.net/juniper/user_activity_info.aspx?id=769http://www.cisco.com/cisco/web/psa/reference.htmlhttp://www.cisco.com/cisco/web/psa/reference.htmlhttp://www.cisco.com/cisco/web/psa/reference.htmlhttp://www.cse.tkk.fi/fi/opinnot/T-110.1100/1999_Tik-110.250/Kalvot/TKK_2_99/index.htmhttp://www.cse.tkk.fi/fi/opinnot/T-110.1100/1999_Tik-110.250/Kalvot/TKK_2_99/index.htmhttp://www.cse.tkk.fi/fi/opinnot/T-110.1100/1999_Tik-110.250/Kalvot/TKK_2_99/index.htmhttp://www.cse.tkk.fi/fi/opinnot/T-110.1100/1999_Tik-110.250/Kalvot/TKK_2_99/index.htmhttp://www.cse.tkk.fi/fi/opinnot/T-110.1100/1999_Tik-110.250/Kalvot/TKK_2_99/index.htmhttp://www.cse.tkk.fi/fi/opinnot/T-110.1100/1999_Tik-110.250/Kalvot/TKK_2_99/index.htmhttp://www.cse.tkk.fi/fi/opinnot/T-110.1100/1999_Tik-110.250/Kalvot/TKK_2_99/index.htmhttp://www.cse.tkk.fi/fi/opinnot/T-110.1100/1999_Tik-110.250/Kalvot/TKK_2_99/index.htmhttp://www.cse.tkk.fi/fi/opinnot/T-110.1100/1999_Tik-110.250/Kalvot/TKK_2_99/index.htmhttp://www.cse.tkk.fi/fi/opinnot/T-110.1100/1999_Tik-110.250/Kalvot/TKK_2_99/index.htmhttp://www.cse.tkk.fi/fi/opinnot/T-110.1100/1999_Tik-110.250/Kalvot/TKK_2_99/index.htmhttp://www.cse.tkk.fi/fi/opinnot/T-110.1100/1999_Tik-110.250/Kalvot/TKK_2_99/index.htmhttp://www.cse.tkk.fi/fi/opinnot/T-110.1100/1999_Tik-110.250/Kalvot/TKK_2_99/index.htmhttp://www.cse.tkk.fi/fi/opinnot/T-110.1100/1999_Tik-110.250/Kalvot/TKK_2_99/index.htmhttp://www.cse.tkk.fi/fi/opinnot/T-110.1100/1999_Tik-110.250/Kalvot/TKK_2_99/index.htm7/27/2019 IP Networking Overview_Issue 1.0
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