OSPF and Loopback Interfaces

Sun, 31 Jul 2011 00:00:00 +0000

I was studying via Google+ Hangout the other day with CJ and Rob, and one of the topics that came up was that OSPFv2 advertises all loopbacks as 32-bit no matter what the configured mask is. I rarely use loopbacks outside of a lab and had no idea it did that, so I set up a quick lab to see for myself. Sure enough! That’s exactly what I saw.

Of course, being the inquisitive network guys that we are, we went on to discuss methods for making OSPF advertise the configured network instead of the single IP. The guys mentioned two methods - to redistribute the connected interfaces and to manually set the OSPF network type on the loopback. We were using IPv4 during the session, but I went back and added some IPv6 addresses and processes to compare.

OSPFv3 - The Basics

Tue, 01 Feb 2011 00:00:00 +0000

A few hours ago, the last of the IPv4 addresses were allocated by IANA. Now’s the time to learn more about IPv6! Yesterday, I posted about EIGRP for IPv6, so I think I’ll continue the trend by introducing OSPFv3, which is the IPv6 implementation of OSPF. As always, I’m using Cisco routers here. Just as yesterday, this is just a guide to the absolutely basics; if you want to do some funky OSPF magic, you won’t find it here - perhaps in time, though.

Ospfv3 on Aaron's Worthless Words

OSPF and Loopback Interfaces

OSPFv3 - The Basics