Exploration Routing Chapter 2(Bupt)

8/2/2019 Exploration Routing Chapter 2(Bupt)

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Cisco ConfidentialPresentation_ID 1

Static Routing

Routing Protocols and Concepts Chapter 2


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Objectives

Define the general role a router plays in networks.

Describe the directly connected networks, differentrouter interfaces

Examine directly connected networks in the routing

table and use the CDP protocol Describe static routes with exit interfaces

Describe summary and default route

Examine how packets get forwarded when using staticroutes

Identify how to manage and troubleshoot static routes


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Context Index

2.1 Router and Network

2.2 Router Configuration Review

2.3 Exploring Directly Connected Networks

2.4 Static Route with Next Hop Address

2.5 Static Routes with Exit Interfaces

2.6 Summary and Default Static Routes

2.7 Managing and Troubleshooting Static Routes

2.8 Static Route Configuration Labs


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2.1 Router and Network


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2.1.1 Role of the Router

Functions of a Router Best Path Selections

Forwarding packets to destination


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2.1.2 Introducing the Topology

Introducing the Topology

3 routers connected via WAN links

Each router connected to a LAN represented by a switch and a PC


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2.1.3 Examining the connection of the Router

Connections of a Router for WAN-A router has a DB-60 port that can support 5 differentcabling standards

Connections of a Router for Ethernet

-2 types of connectors can be used: Straight throughand Cross-over

Straight through used to connect:

-Switch-to-Router, Switch-to-PC, Hub-to-PC, Hub-to-Server

Cross-overused to connect:

-Switch-to-Switch, PC-to-PC, Switch-to-Hub, Hub-to-Hub, Router-to-Router , Router-to-Server


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2.1.3 Examining the connection of the Router


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2.2 Router

Configuration Review


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2.2.1 Examining Router Interfaces

Examining Router Interfaces-Show ip route command used to view routing table

-Show Interfaces command used to show status ofan interface

-Show ip Interface briefcommand used to show aportion of the interface information

-Show running-configcommand used to showconfiguration file in RAM


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shutdown


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2.2.2 Configuring an Ethernet Interface

Unsolicited Messages from IOS


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2.2.2 Configuring an Ethernet Interface

Reading the Routing Table


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2.2.3 Verifying Ethernet interface


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2.2.3 Verifying Ethernet interface

Ethernet interfaces participate in ARP


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2.2.4 Configuring a Serial Interface

Configuring a Serial interface

-Enterinterface configuration mode

-Enter in the ip address and subnet mask

-Enter in the no shutdown command

Example:R1(config)# interface serial 0/0/0interface serial 0/0/0

R1(config-if)# ip addressip address 172.16.2.1 255.255.255.0

R1(config-if)# no shutdownno shutdown


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Physically connecting a WAN Interface

A WAN Physical Layer connection has sides:

Data Circuit-terminating Equipment (DCE) This is the service provider.CSU/DSU is a DCE device.

Data Terminal Equipment (DTE) Typically the routeris the DTE device.


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Configuring serial links in a lab environmentOne side of a serial connection must be considered a DCE

This requires placing a clocking signal use the clock ratecommand.

Example:

R1(config)# interface serial 0/0/0R1(config-if)# clockrateclockrate64000


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2.3 Exploring Directly

Connected Networks


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2.3.1 Verifying Changes the Routing Table

Routing Table Concepts

show ip routeshow ip routecommand reveals the content of therouting table.

Why only have oneConnected Route?


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Observing Routes as They are Added to the Routing Table.


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Remove a Connected Route from Routing Table

Disable debug ip routing by using either the undebug ip routingcommand or the undebug allcommand.


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2.3.2 Devices on Directly Connected Networks

When a router only has its interfaces configured & no other routingprotocols are configured then:

-The routing table contains only the directly connected networks

-Onlydevices on the directly connected networks are reachable


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Pings are discarded


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Purpose of CDP

A layer 2 Cisco proprietary tool used to gather information

about otherdirectly connected Cisco devices.

Concept of neighbors

2 types of neighbors

Layer 3 neighbors

Layer 2 neighbors (CDP operates at Layer 2 only)

2.3.3 Cisco Discovery Protocol (CDP)


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2.3.3 Cisco Discovery Protocol (CDP)

CDP Operation ( 60s 180s)

CDP show commands

Show cdp neighborsShow cdp neighbors

Displays the following information:

Neighbor device ID

Local interface

Holdtime value, in seconds

Neighbor device capability code

Neighbor hardware platform

Neighbor remote port ID

Show cdp neighbors detailShow cdp neighbors detail

-Useful in determining if an IP address configurationerror


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2.3.4 Using CDP for Network Discovery


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2.4 Static Route with

Next Hop Address


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2.4.1 Purpose and Command Syntax of ip route

Purpose ofip route

A manually configured route used when routing from anetwork to a stub network


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2.4.1 Purpose and Command Syntax of ip route

IP route command

To configure a static route use the following command: ip route

Example:


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2.4.2 Configuring Static Route

Installing a Static Route in the Routing Table


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2.4.2 Configuring Static Route

Configuring routes to 2 or more remote networksR1(config)# ip routeip route 192.168.1.0 255.255.255.0 172.16.2.2192.168.1.0 255.255.255.0 172.16.2.2

R1(config)# ip routeip route 192.168.2.0 255.255.255.0 172.16.2.2192.168.2.0 255.255.255.0 172.16.2.2


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2.4.3 Routing Table Principles and Static route

3 Routing principles

PingPC1 to 172.16.2.1PC1 to 172.16.2.2PC1 to PC2PC3 to PC2


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2.4.3 Routing Table Principles and Static route

Finish the configuration


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2.4.4 Recursive Route Lookup

Resolving to an Exit Interface The routerfirst must match static routes destination IP address

with the Next hop address

The next hop address is then matched to an exit interface


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Exit Interface is Down


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2.5 Static Routes with

Exit Interfaces


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2.5.1 Static Route and an Exit Interface Configuring a Static route with an Exit Interface ( )

single search instead of 2 searches. serial point-to-point networks.


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2.5.2 Modifying Static routes Modifying Static routes

Existing static routes cannot be modified. The old static route must bedeleted by placing no in front of the ip route

Example:

nono ip route 192.168.2.0 255.255.255.0 172.16.2.2

A new static route must be rewritten in the configuration


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2.5.3 Verifying the Static Route Configuration

Try it


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2.5.4 Static routes and Ethernet exit interfaces

ARP


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2.6 Summary and

Default Static Routes


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2.6.1 Summary Static Route

Summarizing routes reduces the size of the routing table.

Route summarization is the process ofcombining a number of staticroutes into a single static route.


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2.6.1 Summary Static Route

Configuring a summary static route

Step 1: Delete the current static routeStep 2: Configure the summary static route

Step 3: Verify the new static route


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2.6.2 Default Static Route

Default Static Route

This is a route that will match all packets.

Stub routers that have a number of static routes all exiting the

same interface are good candidates for a default route.

Configuring a default static route

Example:

Router(config)# ip route 0.0.0.0 0.0.0.00.0.0.0 0.0.0.0[exit-interface |

ip-address ]


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2.6.2 Default Static Route

Default static routes and subnet masksSince the subnet mask used on a default static route is 0.0.0.0 allpackets will match.

R1(config)# ip route 0.0.0.0 0.0.0.0 serial 0/0/0ip route 0.0.0.0 0.0.0.0 serial 0/0/0


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Verifying a Default Static Route

Before


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2.7 Managing andTroubleshooting Static

Routes


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2.7.1 Static Routes and Packet Forwarding

The following is an example of the packet forwarding process with staticroutes. As you can see in the animation, PC1 is sending a packet to PC3:

1. The packet arrives on the FastEthernet 0/0 interface of R1.

2. R1 does not have a specific route to the destination network, 192.168.2.0/24; therefore, R1uses the default static route.

3. R1 encapsulates the packet in a new frame. Because the link to R2 is a point-to-point link, R1adds an "all 1s" address for the Layer 2 destination address.

4. The frame is forwarded out the serial 0/0/0 interface. The packet arrives on the Serial 0/0/0interface on R2.


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2.7.1 Static Routes and Packet Forwarding

The following is an example of the packet forwarding process with staticroutes. As you can see in the animation, PC1 is sending a packet to PC3:

5. R2 decapsulates the frame and looks for a route to the destination. R2 has a static route to192.168.2.0/24 out Serial0/0/1.

6. R2 encapsulates the packet in a new frame. Because the link to R3 is a point-to-point link,R2 adds an "all 1s" address for the Layer 2 destination address.

7. The frame is forwarded out the Serial0/0/1 interface. The packet arrives on the Serial0/0/1interface on R3.

8. R3 decapsulates the frame and looks for a route to the destination. R3 has a connected routeto 192.168.2.0/24 out FastEthernet 0/1.


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2.7.1 Static Routes and Packet Forwarding The following is an example of the packet forwarding process with static routes.

As you can see in the animation, PC1 is sending a packet to PC3:

9. R3 looks up the ARP table entry for 192.168.2.10 to find the Layer 2 MAC address forPC3.

a. If no entry exists, R3 sends anARPrequest out FastEthernet 0/0.

b. PC3 responds with anARP reply which includes the PC3 MAC address.

10. R3 encapsulates the packet in a new frame with the MAC address of interfaceFastEthernet 0/0 as the source Layer 2 address and the MAC address of PC3 as thedestination MAC address.

11. The frame is forwarded out the FastEthernet 0/0 interface. The packet arrives on the

NIC interface of PC3.


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2.7.2 Troubleshooting a Missing Route

Tools that can be used to isolate routing problemsinclude:

-Ping tests end to end connectivity

-Traceroute used to discover all of the hops (routers)

along the path between 2 points-Show ip route used to display routing table & ascertainforwarding process

-Show ip interface brief used to show status of router

interfaces

-Show cdp neighbors detail used to gather configurationinformation about directly connected neighbors


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2.7.3 Solving a Missing Route

Finding a missing or mis-configured route requires

methodically using the correct tools.

-Start with PING. If ping fails then use tracerouteto

determine where packets are failing to arrive

Issue: show ip routeto examine routing table.

-If there is a problem with a mis-configured static route

remove the static route then reconfigure the new static

route


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2.7.3 Solving a Missing Route

R2(config)# no ip route 172.16.3.0 255.255.255.0serial0/0/1

R2(config)# ip route 172.16.3.0 255.255.255.0serial 0/0/0


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2.8 Static Route

Configuration Labs


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Summary Routers

-Operate at layer 3-Functions include best path selection & forwardingpackets

Connecting Networks

WANsSerial cables are connected to router serial ports.

In the lab environment clock rates must be configuredfor DCE

LANs

Straight through cables or cross over cables are usedto connect to fastethernet port. (The type of cableused depends on what devices are being connected)

Cisco Discovery Protocol

A layer 2 proprietary protocol


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Summary Static Routes

-This is a manually configured path that specifies how the router will getto a certain point using a certain path.

Summary static routes-This is several static routes that have been condensed into a singlestatic route.

Default route

-It is the route packets use if there is no other possible match for theirdestination in the routing table.

Forwarding of packets when static route are used-Zinins 3 routing principles describe how packets are forwarded

Troubleshooting static routes may require some of the followingcommands:

-Ping

-Traceroute

-Show IP route

-Show ip interface brief

-Show cdp neighbors detail


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Exploration Routing Chapter 2(Bupt)

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