Cisco IOS and the "network" statement

This has to be the second-most misunderstood statement. Here's how it works.

Each routing process maintains its own routing table. So there is a table for BGP, a table for OSPF, a table for RIP, a table for static routes, a table for routes to connected interfaces and so on.

There is a forwarding table. This determines the next-hop of packets flowing through the router.

Entries in the routing table are placed into the forwarding table. If two routes clash then the routing protocol with the better "administrative distance" wins: connected > static > exterior routes > interior routes.

Entries in the forwarding table are placed in a routing table is there is an exactly matching "network" statement in the routing process's configuration and the entry in the forwarding table wasn't put there by this routing process.

Let's take the trivial case, a connected interface

interface Ethernet0
 ip address 1.2.3.4 255.255.255.0

router ospf 65000
 network 1.2.3.0 0.0.0.255

You often see this

ip route 1.2.3.0 0.0.0.255 1.2.3.255

router ospf 65000
 redistribute static

Don't do that, do this:

ip route 1.2.3.0 0.0.0.255 1.2.3.255

router ospf 65000
 network  1.2.3.0 0.0.0.255

Getting rid of the "redistribute" statement removes a common cause of routing loops. "Redistribute" should really be a hidden command, it's only useful for people who know what they are doing.

Halloween

The kids got all dressed up, E looked very fine as a vampire. Then they all trooped off to knock on the doors of their friends. Large amounts of lollies collected. Stomach aches complained of (surely there's no connection!).

Had a huge bag near our door should adventurous older kids wander down our street and be attracted by the ghost and spiders on the front gate. There were a few callers. A nice time was had by all.

As usual, I find myself holding the completely different view that I had before we had kids. B.K I thought Halloween was a horrible US import. A.K I think that it does no harm, so let them dress up and have some fun.