Routing - things I should have known

Funny how you go through life thinking that you know an awful lot, only to find out that you don't know nearly as much as you did, making you question everything you actually do know...

Anyhow, I was reading up on static routes for the CCNA tonight. Breezing over things, I saw something that I had never really considered before, though I instantly saw how this was going to help me do my job a little better.

I thought there was not much more to a static route entry than to specify the network you wanted to route to, the netmask and the IP address to send that traffic toward. For instance:

ip route 192.168.1.0 255.255.255.0 10.1.1.1

sends anything destined for the 192.168.1.0/24 network to an interface with IP address 10.1.1.1. Woo-hoo, right? Well, now I've learned about Floating Static Routes. By adding a parameter at the end of the ip route statement, you can set the administrative distance for the route than the default value of 1 for a statically-assigned route. So now our command becomes:

ip route 192.168.1.0 255.255.255.0 10.1.1.2 2

The "2" at the end of that statement makes this route slightly higher in administrative distance, and that route will not be added to the routing table unless the first route goes down. This is useful if you have multiple links to get to the same location, such as two different ISP's (multiple default routes) or multiple paths to your remote offices. So, along with that, let's run down the default administrative distances for ip routes in Cisco IOS:

Route type Administrative distance
==============================================
Connected interface 0
Static route 1
EIGRP summary 5
External BGP 20
Internal EIGRP 90
IGRP 100
OSPF 110
IS-IS 115
RIP (v1 and v2) 120
EGP 140
External EIGRP 170

When a router learns of the same destination through multiple routing protocols, it will choose the path with the lowest administrative distance.

Perhaps more later. I've been solidifying my understanding of the show ip route output today, also, but like I said...I feel like I should know this stuff already. Ah well, it's good to learn and better to know what the heck you're talking about should a client ask "What does that number mean there, after the IP address?"

Good night, all.