Wednesday, June 28, 2006
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.
Tuesday, June 20, 2006
RIP distribute lists deny specific route advertisements. RIP offset-lists increase the metric (hopcount) for specific route advertisements.
Sunday, June 18, 2006
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
Monday, June 12, 2006
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
We cable and configure ethernet and synchronous serial point-to-point links. In the next session these will be the "legs" of our triangle.
Wednesday, June 7, 2006
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.
Friday, June 2, 2006
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.