RD-CSY2001-08/09

Distance Vector Routing Protocols

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Characteristics of Distance Vector Routing protocols. Network discovery process using Routing Information

Protocol (RIP). Identify the conditions leading to a routing loop and

explain the implications for router performance. Recognize that distance vector routing protocols are in use

today

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Function(s) of Dynamic Routing Protocols:◦ Dynamically share

information between routers.

◦ Automatically update routing table when topology changes.

◦ Determine best path to a destination.

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Criteria used to compare routing protocols includes Time to convergence Scalability Resource usage Implementation & maintenance

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Algorithm - procedure for accomplishing a certain task

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Two Main Approaches Distance Vector Protocols

◦ E.g., RIP (Routing Information Protocol) Link State Protocols

◦ E.g., OSPF (Open Shortest Path First) Our Focus

◦Distance Vector Protocols - RIP

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A router using distance vector routing protocols knows 2 things:

Distance to final destination

Vector, or direction, traffic should be directed

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Characteristics Periodic updates Triggered updates Exchange information

with Neighbors Entire routing

table is included with routing update

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Triggered Updates◦Conditions in which

triggered updates are sent Interface changes state Route becomes

unreachable Route is placed in

routing table

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Initial Exchange of Routing Information◦ If a routing protocol is configured

then routers will exchange routing information

Routing updates received from other routers◦ Router checks update for new

information If there is new information

Metric is updated New information is stored in

routing table

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Regular Time Intervals in which a router sends out its entire routing table to its neighbours.

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RIP uses 4 timers◦ -Update timer ◦-Invalid timer ◦-Holddown timer ◦-Flush timer

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Exchange of Routing Information◦ Router convergence is

reached when All routing tables in the

network contain the same network information

◦ Routers continue to exchange routing information If no new information is

found then Convergence is reached

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• Using router rip and network commands to • enable RIP.

• Enabling RIP on an IP-addressed network.

• Monitoring IP packet flow using the show IP • protocol command.

• The show ip route command.

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• debug ip rip• show ip rip database • show ip protocols {summary} • show ip route • debug ip rip {events} • show ip interface brief

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