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Best practises

If running management loopbacks on a network, is it better practise to leave the loopbacks as /32 or put them into their own network e.g /28 ?

I'm configuring my loopbacks as /32 putting the passive interface command for the loopbacks under rip ... however, the loopbacks are still getting advertised, I thought passive interface was supposed to suppress this, or is it because they are /32 .... it's annoying as I've over 34 loopbacks and they obviously show up when i do a sh ip route .... is it more correct to have my loopbacks in their on network with a /26 ?


Re: Best practises

Passive interface only prevents advertisements from being processed out of the interface. The network connected to the interface will still be advertised out other interfaces. Changing the subnet mask will probably make your situation worse since the network represented by the subnet mask will be advertised all over the place.

Your best bet is to use a distribute list. Assuming your loopback address is, do the following:

router rip

network (enter network statements)

distribute-list 1 out

access-list 1 deny host

access-list 1 permit any




Re: Best practises

It doesn't matter whether they are in a /32, or in a subnet, as long as either way fits into what you want to see in your routing table. You can, of course, make them /28's, or whatever, as long as you are in the same major net as your other rip routes, etc.... The normal classful routing protocol rules.

Note that passive only prevents rip from sending updates out an interface, it doesn't stop the interface from being advertised. If you don't want rip to advertise these interfaces, then you will need to move them into another major network, not covered by the rip network statements configured. Unlike eigrp and ospf, rip doesn't allow wildcard bits so it can run on a subset of interfaces within a major net, or a superset of interfaces within multiple major nets. This capability has nothing to do with the classful nature of the routing protocol, it's just never been coded for rip.

I'm curious how you would use these interfaces for management of the routers if you couldn't get to them, though (?). :-)


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