/128 IPv6 prefixes in the wild?

Mark Tinka mtinka at globaltransit.net
Thu Dec 15 16:13:17 UTC 2011

On Thursday, December 15, 2011 09:56:04 PM Brian Johnson 

> I think you will learn a lot of /128s from IGP, but not
> from eBGP. I consider the "wild" to be the DFZ or
> similar type of network and in that case, you should not
> see advertisements for anything longer than a /48. This
> is not hard and fast, but please correct me if I'm
> wrong.

Ideally, yes.

Good filtering (against your peers, customers and upstreams) 
will ensure you keep anything longer than a /48 out of your 

However, do note that if you provide customer-induced 
automated blackhole routing (where customers attach an 
"evil" community to an "evil" host route and send that to 
you in an eBGP update because you expect it), that's one 
other way to see /128's (or more appropriately, something 
longer than a /48) across eBGP sessions with customers.

Also, if customers multi-home to you and they want to be 
able to load share traffic across the various links between 
their network and yours, you may be inclined to allow them 
to send longer subnets that have a NO_EXPORT community 
attached to them so that load sharing occurs within your 
network for their inbound traffic, but de-aggregated routes 
do not flood the rest of the Internet. This is another way 
you could get "longer" routes into your network, with the 
benefit of not polluting the global Internet.

Among other scenarios... :-).

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