[135989] in North American Network Operators' Group
Re: IPv6: numbering of point-to-point-links
daemon@ATHENA.MIT.EDU (Blake Hudson)
Mon Jan 31 12:14:46 2011
Date: Mon, 31 Jan 2011 11:13:08 -0600
From: Blake Hudson <blake@ispn.net>
To: nanog@nanog.org
In-Reply-To: <4D3DA762.33E4.0097.1@globalstar.com>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
> All of the (mostly religious) arguments about /64 versus any
> smaller subnets aside, I'm curious about why one would choose
> /126 over /127 for P-to-P links? Is this some kind of IPv4-think
> where the all-zeros and all-ones addresses are not usable
> unicast addresses? This isn't true in IPv6 (of course, it's not
> strictly true in IPv4 either). Is there another reason?
I setup a p2p /127 link and found that BGP would not peer over the link;
Changing to /126 resolved the problem. I never looked into it further
because I had intended to use /126 from the start. My guess is that
while BGP should be a unicast IP, Cisco's implementation uses an anycast
in some cases, disregarding the configured unicast address.
Just one practical example...
