I have some IOS devices which don't carry a full IPv4 table. For IPv4, they are learning default route via IBGP.
For IPv6, is it best practice to learn default via IBGP, or IGP? I have worked in shops that distribute IPv4 default in IPG, IBGP, or both.
Also, I saw one note suggesting use of 2003::/3 instead of ::/0 ?
Wouldn't that really be dependent on how your IGP and IBGP are set up in your particular shop? How routes are redistributed into each routing process, etc? Also what your intentions traffic engineering and redundancy wise are. For instance, if you're connected to multiple ISPs at multiple locations, you might want your inet traffic taking an alternate route if your shortest path goes down, in which case it'd seem you'd want your default coming from the IBGP or IBGP default distributed into your IGP.
But then, I'm not BGP ace, so I'd also be interested in a more expert opinion.
I think the use of 2000::/3 instead of ::/0 is based on some bug in a particular OS. I personally use ::/0 with no issues. More accurately, radvd advertises ::/0, not the other.