/128 IPv6 prefixes in the wild?
mtinka at globaltransit.net
Thu Dec 15 10:13:17 CST 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
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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