PACE-IT: Introduction to Routing Protocols - N10 006

Introduction to routing protocols.

Instructor, PACE-IT Program – Edmonds Community College

Areas of Expertise Industry Certification

PC Hardware

Network Administration

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M.B.A., IT Management, Western Governor’s University

B.S., IT Security, Western Governor’s University

Entrepreneur, executive leader, and proven manger with 10+ years of experience turning complex issues into efficient and effective solutions.

Strengths include developing and mentoring diverse workforces, improving processes, analyzing business needs and creating the solutions required— with a focus on technology.

Brian K. Ferrill, M.B.A.


– Interior vs. exterior gateway routing protocols.

– More routing concepts.

– Routing protocols.

PACE-IT.

Interior vs. exterior gateway protocols.Introduction to routing protocols.

Interior vs. exterior gateway protocols.

– Interior Gateway Protocol (IGP).» A category of protocols used within autonomous

networks.• Used between networks that you can control.

» The most popular IGP protocols are OSPF (Open Shortest Path First) and RIPv2 (Routing Information Protocol version 2).

» Special mention: IS-IS (Intermediate System to Intermediate System), which is popular with extremely large autonomous networks like an ISP’s network.

– Exterior Gateway Protocol (EGP).» A category of protocols used between non-

autonomous networks.• The type of routing protocol used between

networks under separate control.» The most popular EGP protocol is Border Gateway

Protocol (BGP).



It is not uncommon for organizations to have more than one network that they are routing traffic between. These are called autonomous networks.

Some IGP routing protocols use an administrator defined autonomous system (AS) number as one means of identifying which networks can directly communicate with each other.

The AS is not a metric, but a means of identifying a network that might possibly accept another network’s traffic.

Remember, the AS is only significant within autonomous networks and has no relevance outside of them.


More routing concepts.Introduction to routing protocols.

More routing concepts.

– Classification of routing protocols.

» IGP and EGP routing protocols can be broken out into three other categories of protocols, which is designated by their main method of determining routes between networks.

» Distance-vector routing protocols.• Routes are determined by how many routers

exist between the source and the destination. The efficiency of the links in the selected route is not taken into consideration.

• Periodically, the whole routing table is broadcasted.

» Link state routing protocols.• Metrics are used to determine the best possible

route between destinations. The protocol then only monitors the state of directly connected links and only makes changes when changes to links occur.

• Only changes in link status are broadcasted.» Hybrid routing protocols.

• Use aspects of both the distance vector and link state routing protocols.



– Next hop.» The next router in the path between two points.

• Is often designated by an interface address of the device that is receiving the data, or by the router’s name, or by the router’s location.

– Routing table.» The database table that is used by a router to

determine the best possible route between two points.

» Different routing protocols use different algorithms to place routes in the table.

– Convergence (steady state).» The amount of time that it takes all of the routers

in an autonomous system to learn all of the possible routes within that system.

• Faster convergence times are desirable.


Routing protocols.Introduction to routing protocols.

Routing protocols.

– Routing Information Protocol v2 (RIPv2).

» An IGP (autonomous) distance-vector protocol.• A hop count of 16 is considered unreachable.

» Uses various methods, including hop count to reduce the chances of a routing loop.

» Uses multicast to advertise routing tables (224.0.0.9).

– Open Shortest Path First (OSPF).» An IGP link state routing protocol.» Uses Dijkstra’s algorithm to determine the shortest

path to a network.» After initial startup, it only advertises changes to its

routing table, making convergence faster.» Uses different types of link state advertisements (LSAs)

to announce different changes or operations.• Uses multicast addresses 224.0.0.5 or 224.0.0.6,

depending on the type of LSA.


Routing protocols.

– Intermediate System-to-Intermediate System (IS-IS).

» An IGP link state routing protocol.» Similar to OSPF in operation.

• It uses Dijkstra’s algorithm as well, but also uses different metrics to determine the best path.

» Highly scalable and offers fast convergence.» Often found used within networks under the control of

an ISP.

– Border Gateway Protocol.» An EGP (non-autonomous) hybrid routing protocol.» Considered the routing protocol of the Internet.» It can be considered a path-vector protocol.

• One of the metrics used is the number of autonomous systems that must be crossed (not individual routers).

» Highly scalable, but it has very slow convergence times when changes occur.


Routing protocols.

Enhanced Interior Gateway Routing Protocol (EIGRP) is an advanced distance-vector (hybrid) IGP routing protocol developed by Cisco.

In 2013, Cisco made EIGRP an open source routing protocol in an effort to increase its use in autonomous networks. It uses aspects of both the distance-vector protocols and link state protocols to build its routing table. EIGRP has very fast convergence times.

EIGRP uses a Neighbor Table (directly connected routers) and a Topology Table to build its routing table. The protocol only announces changes to the routing table (on multicast address 224.0.0.10) in order to reduce bandwidth consumption.


What was covered.Introduction to routing protocols.

IGP routing protocols are used within autonomous networks (networks under the control of a single organization). BGP routing protocols are used between non-autonomous networks. Some IGP protocols use an AS number to help determine which networks can connect with each other.

Topic


Summary

IGP and EGP routing protocols can be broken into three types: distance-vector protocols, link state protocols, and hybrid protocols. Their classification is determined by how they operate. The next hop is the next router in the path of a route. The routing table is a database of all known routes from the perspective of the router. Convergence is when the network has reached a steady state.


RIPv2 is a distance-vector routing protocol that only cares about the number of hops between the source and destination. OSPF and IS-IS are link state routing protocols that use the Dijkstra algorithm. BGP is a hybrid path-vector routing protocol and is considered the routing protocol of the Internet. EIGRP is an advanced distance-vector (hybrid) routing protocol developed by Cisco.

Routing protocols.

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PACE-IT: Introduction to Routing Protocols - N10 006

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Transcript of PACE-IT: Introduction to Routing Protocols - N10 006