[121685] in North American Network Operators' Group
Re: Using /126 for IPv6 router links
daemon@ATHENA.MIT.EDU (Glen Turner)
Sun Jan 24 19:42:49 2010
Date: Mon, 25 Jan 2010 11:12:04 +1030
From: Glen Turner <gdt@gdt.id.au>
To: Owen DeLong <owen@delong.com>
In-Reply-To: <D7706517-BF0C-4979-A377-9467F26B33E9@delong.com>
Cc: nanog@nanog.org, Mathias Seiler <mathias.seiler@mironet.ch>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On 24/01/10 12:54, Owen DeLong wrote:
> Use the /64... It's OK... IPv6 was designed with that in mind.
I'd suggest using a /126. For two reasons.
1) Using EUI-64 addresses on router-router links is an error, the
consequences of which you encounter the first time you replace
some faulty hardware.[1] I have made this error :-( If you
are not using EUI-64 then assigning a non-autoconf /64 is no
less or more work than assigning a non-autoconf /126.
2) Having a block of addresses for router-router links (and other blocks
for other infrastructure such as loopbacks and unicast) makes ACLs
much simpler. Using a /126 means that this block can last for a long,
long time, reducing configuration maintenance.
Cheers, Glen
[1] Basically, interface addresses end up scattered through the
router's configuration (some manufacturers are better than
others in this regard). Tracking down all the references to
an address and changing the config merely as the result of a
hardware swap is painful and adds complexity at a time when
it is not desired.
--
Glen Turner <http://www.gdt.id.au/~gdt/>
Network Engineer
Australia's Academic & Research Network <http://www.aarnet.edu.au/>
