Wednesday, June 28, 2006

IGRP: Interior Gateway Routing Protocol

IGRP is a Cisco-proprietary routing protocol. It is a classful distance vector protocol with a metric based on bandwidth and delay. This is superior to RIP, whose metric is based on hop-count. IGRP's classfulness makes it a bad choice for new deployments, but its advanced metric is worth study.

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Tuesday, June 20, 2006

RIPv1 distribute lists and offset-lists

RIP distribute lists deny specific route advertisements. RIP offset-lists increase the metric (hopcount) for specific route advertisements.

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Sunday, June 18, 2006

Problems with RIP Version 1

RIP version 1 route advertisements do not include a field for the netmask. This means receiving routers have to gess the netmask based on whatever information they have available. That includes the "natural" netmask of that classful network. That also includes the receiving routers own configuration.

This means that variable length subnets and discontiguous classful network have problems with RIP version 1. The lack of the netmask field in the route advertisement is a real problem.

Friday, June 16, 2006

RIP Version 1

RIP version 1 is a classful routing protocol. We cover the RIP packet format and configuration. We see examples of split horizon and triggered updates using the RIP debug commands.

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Monday, June 12, 2006

Static routing and introduction to CEF

Routing protocols (and static routing) update the route table. The route table is used to forward packets. Cisco Express Forwarding (CEF) is a special route table optimized to forward packets more efficiently.

Saturday, June 10, 2006

Serial and ethernet point-to-point links

We cable and configure ethernet and synchronous serial point-to-point links. In the next session these will be the "legs" of our triangle.

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Wednesday, June 7, 2006

Classful IP addressing

Routers route packets based on the destination IP address: a 32-bit number included in the header of every IP packet. Historically, "large" sites were allocated IP address blocks starting with 0 (binary). Medium sites were allocated address blocks starting with the bits 10. "Small" sites were allocated address blocks starting with the bits 110.

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Friday, June 2, 2006

Cisco 2500 password recovery

Every network engineer needs to be able to deal with a router with an unknown password. Whether you are taking over a site where the previous engineer was "hit by a bus", or scrounging routers from the storage closet, good network engineers can deal with routers with unknown passwords.

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Thursday, June 1, 2006

Scrounging Cisco Gear and Using the Console

You can best take advantage of the Cisco training podcast series by getting routers and following along. First you need to scrounge or buy routers and cables. This episode helps you decide what to get. This episode also explains how to access the console.

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