IPv6 dual stacking and route tables

Ryan Rawdon ryan at u13.net
Fri Feb 3 21:44:33 UTC 2012

On Feb 3, 2012, at 3:25 PM, Philip Dorr wrote:

> You should accept the full v6 table, because some IPs may not,
> currently, be reachable via one of the carriers.

Definitely agreed here, and this is why we take full v6 tables.  Especially since one of our upstreams does not peer with at least one other large network; if we took just a default from them, we would likely be sending them traffic which they in turn do not have a route for whereas the other upstream of ours does.

> On Fri, Feb 3, 2012 at 2:10 PM, -Hammer- <bhmccie at gmail.com> 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-
>> "I was a normal American nerd"
>> -Jack Herer

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