Quick IP6/BGP question

George, Wes E IV [NTK] Wesley.E.George at sprint.com
Mon May 24 18:41:08 UTC 2010

We've done it both ways.
We've found that there are sometimes issues with announcing IPv6 NLRI over IPv4 BGP sessions depending on your chosen vendor and code version on both sides of the session. Specifically, we have seen some implementations where an IPv4-mapped IPv6 address (usually the IPv4 router-id or neighbor address) is announced as the next-hop, or a link-local address is used as the next-hop, or some random junk is announced as the next-hop, even with next-hop-self configured. All of these result in the receiving router dropping the announcements because it doesn't have a route to the next-hop. It's usually possible to work around this by using route policies to force the correct next-hop to be written on in/outbound announcements, and as we find it working improperly, we've been reporting bugs, but I thought it would be worth bringing this up as a caveat so that you can make sure your hardware/software of choice is behaving properly if you choose to go this route.
Also, I know of at least one vendor that didn't implement the converse functionality in CLI yet - it's impossible to configure an IPv6 neighbor address in the IPv4 address family in order to exchange IPv4 NLRI over an IPv6 BGP session.

Wes George

-----Original Message-----
From: Thomas Magill [mailto:tmagill at providecommerce.com]
Sent: Monday, May 24, 2010 2:22 PM
To: nanog at nanog.org
Subject: Quick IP6/BGP question

>From the provider side, are most of you who are implementing IP6
peerings running BGP over IP4 and just using IP6 address families to
exchange routes or doing IP6 peering?

Thomas Magill
Network Engineer

Office: (858) 909-3777

Cell: (858) 869-9685
mailto:tmagill at providecommerce.com <mailto:tmagill at providecommerce.com>

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