[AusNOG] Whats peoples BCP for Unused IP Space on Routers ?

[Shaun Deans]

Morning Noggers ?

I'm looking for some quick feedback on what peoples BCP (Best Common
Practice) is when it comes to unused ip space. For example if you have
the ip range 1.2.3.0/24 and you only have 1.2.3.0/25 active/routed
what do you do with 1.2.3.128/25.

I have seen many techniques including:
- ACLs (Bad IMHO as it requires CPU cycles)
- Tying to a Loopback (Bad: Leaves ip's open on router which require acls/cpu)
- Null routing ( would be my pick)
- Nothing at all (Very Bad as it would bubble up causing routing loops)

Gave it a google and there were no real BCP's that stood out so im
interested to hear what everyone else does ?

Cheers

S