IPv6 dual stacking and route tables

Jeroen Massar jeroen at unfix.org
Fri Feb 3 20:47:00 UTC 2012

On 2012-02-03 21:37 , -Hammer- wrote:
> Thanks Jeroen (and Ryan/Philip/Cameron/Justin/Etc.) for all the online
> and offline responses. That was fast. The struggle is that I'm having
> trouble seeing how/why it would matter other than potential latency on
> the IPv4 side. IPv6 conversations usually involve taking the full table
> when dealing with multi-homed/multi-site setups. IPv4 I didn't really
> consider (taking the full table) until I mentioned this to some of my
> vendors technical folks and it caused a lot of reflection. Not on the L3
> part. Just on the DNS part. This appears to be a tough subject area when
> it comes to V4/V6 deployment strategies. The bottom line is that I'll
> take whatever the carrier feeds in V6. Just trying to see where I would
> be missing out by not doing the same in V4. Again, I have the hardware
> to support it and I really have no reason not to do it. I just want to
> be able to justify to myself why I'm doing it.

Why you want non-defaults in both IPv4 and IPv6:
 - more possible paths
 - less chances of blackholes.

And of course, those paths will be more stable and you don't get
hot-potato swapping between two defaults.

And that in turn allows the Happy Eyeballs mechanisms to do their jobs
much better as they keep a history per host or prefix, they assume IPv6
/48's and IPv4 /24's from what I have seen, in some cases.


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