Comcast enables 6to4 relays

Franck Martin franck at
Tue Aug 31 07:20:09 UTC 2010

I think this

may answer some of the questions on how to make it work correctly.

I like the fact the 6to4 gateway should be on a separate machine that BGP with the main router. If the gateway dies, the routes are withdrawn and clients go and look for another gateway somewhere else....

----- Original Message -----
From: "Jeroen Massar" <jeroen at>
To: "Mitchell Warden" <wardenm at>
Cc: nanog at
Sent: Tuesday, 31 August, 2010 6:46:52 PM
Subject: Re: Comcast enables 6to4 relays

On 2010-08-31 08:22, Mitchell Warden wrote:
> Is there a reason not to advertise more specific prefixes from 2002::/16 to ensure that traffic for your v4 routes comes back to your own 6to4 router?
> If for example all my users have v4 addresses in, I could advertise 2002:C002:0000::/40 instead of or in addition to the full 2002::/16.

The RFC forbids that with a good reason, as then we'll end up importing
the IPv4 BGP table into IPv6... not something we want to see (unless one
loves to import 300k routes in there, I guess people will really start
whining about that though ;).


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