Re: IPv6 dual stacking and route tables

[Ryan Rawdon <ryan () u13 net>]

On Feb 3, 2012, at 3:10 PM, -Hammer- wrote:

> So, we are preparing to add IPv6 to our multi-homed (separate routers and carriers with IBGP) multi-site business. 
> Starting off with a lab of course. Circuits and hardware are a few months away. I'm doing the initial designs and 
> having some delivery questions with the carrier(s). One interesting question came up. There was a thread I found (and 
> have since lost) regarding what routes to accept. Currently, in IPv4, we accept a default route only from both 
> carriers at both sites. Works fine. Optimal? No. Significantly negative impact? No. In IPv6, I have heard some folks 
> say that in a multi-homed environment it is better to get the full IPv6 table fed into both of your edge routers. Ok. 
> Fine. Then, The thread I was referring to said that it is also advisable to have the entire IPv4 table fed in 
> parallel. Ok. I understand we are talking about completely separate protocols. So it's not a layer 3 issue. The 
> reasoning was that DNS could potentially introduce some latency.
>
> "If you have a specific route to a AAAA record but a less specific route to an A record the potential is for the trip 
> to take longer."
>
> That was the premise of the thread. I swear I googled it for 20 minutes to link before giving up. Anyway, can anyone 
> who's been thru this provide any opinions on why or why not it is important to accept the full IPv6 table AND the 
> full IPv4 table? I have the hardware to handle it I'm just not sure long term what the reasoning would be for or 
> against. Again, I'm an end customer. Not a carrier. So my concern is (A) my Internet facing applications and (B) my 
> users who eventually will surf IPv6.
>
> Any guidance would be appreciated. Thanks.
>
> -Hammer-

We have been accepting our upstreams' connected and customer routes only (v4) and full routes (v6) without issue.  I 
can't say that I have previously heard of the DNS performance example/concern you provided above