Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

Routing Protocols and Concepts

CH5: RIP V1

Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

Notes

• If you see any mistake’s’ on my PowerPoint slides or if you have any other questions or comments, please feel free to email me at abdu.elsaid@yahoo.com.

Thanks! Abdelkhalik Elsaid MousaFCI – SCU - EgyptCisco Networking Academy

Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

RIPv1 History and Characteristics

• GWINFO (Mid 1970 Xerox), RIP (XNS BSD), RIP V1(RFC 1988), RIP V2(1994), RIP ng(1997)

• RIP is a distance vector routing protocol.• Metric: hop count, Advertised routes with metric > 15 are

unreachable.• Messages are periodic and broadcast every 30 seconds.

Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

RIPv1 Message Format

Command

Version Address Family Identifier IP Metri

c

Data Src. port Dest. port

UDP Datagram Src. IP Dest.

IP Protocol

Packet Src. MAC

Application

Transport

Internet

Network Access Dest. MAC

Max 25 Routes 512 B

Route Entries

Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

RIP Request / Response Process• On startup, The router requests the full routing table.• A response message is sent back by RIP-enabled neighbors.• The startup router then sends a triggered update out all RIP-

enabled interfaces containing its own routing table.

Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

IP Address Classes and Classful Routing

• RIP v1 is a classful routing protocol.• So, a router either uses the subnet mask configured on a local

interface, or applies the default subnet mask. • RIPv1 networks cannot be discontiguous nor can support VLSM.

Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

Administrative Distance• AD is the trustworthiness (or preference) of the route source. • RIP AD is 120.

ح�طاما ومستقبلك جحيما حاضرك ستحيل ألنها ماضيك أخطاء عند كثيرا تقف ال ،والصواب الحق طريق في جديدة دفعة تعطيك اعتبار وقفة منها يكفيك

SHOW IP ROURE

SHOW IP PROTOCOLS

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Basic RIPv1 Configuration: Scenario A

Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

Enabling RIP: router rip

does not start RIP process. It provides access

to configure the routing protocol.

No router rip: stops the RIP

process and erases all existing

RIP configurations

Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

Specifying Networks

What happens If you enter a

subnet or an interface address?

Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

Verifying RIP: Show ip route

Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

Verifying RIP: Show ip protocols

Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

Verifying RIP: debug ip rip

Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

Passive Interfaces• Unnecessary RIP Updates Impact Network

1. Bandwidth is wasted transporting unnecessary updates. 2. All LAN devices process the update up to Transport layers.3. Advertising updates on a broadcast network is a security risk.

• Stopping Unnecessary RIP Updates: R2(config-router)#passive-interface f0/0.

no network

Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

Automatic Summarization: Scenario B

On certification exams, entering a subnet address instead of the classful network address in a network

command is considered an incorrect answer.

Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

Boundary Routers and Automatic Summarization

• Boundary Router: is a router that has interfaces in more than one major classful network.

• RIP is a classful routing protocol that automatically summarizes classful networks across major network boundaries.

Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

Processing RIP Updates• The following two rules govern RIPv1 updates:

IF a routing update and the interface on which it is received belong to the same major network

THEN the subnet mask of the interface is applied to the network in the updateELSE the classful subnet mask of the network is applied.

Debug ip ripDebug ip routing

Routers running RIPv1 are limited to using the same subnet mask for all subnets with the same classful network

Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

Advantages/Disadvantage of Automatic Summarization

• Advantages of Automatic Summarization1. Conserve bandwidth, smaller routing updates sent & received. 2. Minimized routing table and then faster lookup.3. Stability in routing table.

• Disadvantages of Automatic Summarization1. Does not support discontiguous networks.

A network is

separated by another network

Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

Discontiguous Topologies do not Converge with RIPv1

R1 does not have any routes to the LANs attached to R3 R3 does not have any routes to the LANs attached to R1

R2 has two equal-cost paths to the 172.30.0.0 network

Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

Default Route and RIPv1: Scenario C

Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

Propagating the default route in RIPv1

Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy

Thank You..