RE: Quick IP6/BGP question

["George, Wes E IV [NTK]" <Wesley.E.George () sprint com>]

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.

Thanks,
Wes George

-----Original Message-----
From: Thomas Magill [mailto:tmagill () providecommerce com]
Sent: Monday, May 24, 2010 2:22 PM
To: nanog () 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

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


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