Best practices IPv4/IPv6 BGP (dual stack)

Owen DeLong owen at
Sat May 3 00:09:54 UTC 2014

On May 2, 2014, at 12:44 PM, Deepak Jain <deepak at> wrote:

> Between peering routers on a dual-stacked network, is it considered best practices to have two BGP sessions (one for v4 and one for v6) between them? Or is it better to put v4 in the v6 session or v6 in the v4 session?

Separate v4 and v6 sessions are the best practice. It is possible to have a single-protocol outage in which case you either take out the other protocol unnecessarily or you black-hole traffic.

> According to docs, obviously all of these are supported and if both sides are dual stacked, even the next-hops don't need to be overwritten.

Mostly true, but implementations vary and YMMV vendor to vendor and in some cases, model and/or software version to model and/or software version. Two sessions always works and unless you are somehow resource-constrained on sessions is really the simplest, easiest to manage, cleanest way to do things.

> Is there any community-approach to best practices here? Any FIB weirdness (e.g. IPv4 routes suddenly start sucking up IPv6 TCAM space, etc)  that results with one solution over the other?

See above for BCP. As to the rest, in my experience, the answers vary (see above).


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