RE: Failover IPv6 with multiple PA prefixes (Was: IPv6 fc00::/7 — Unique local addresses)

["George Bonser" <gbonser () seven com>]

> From: Jeroen Massar > Sent: Thursday, October 21, 2010 9:57 AM
> To: Allen Smith
> Cc: NANOG list
> Subject: Failover IPv6 with multiple PA prefixes (Was: IPv6 fc00::/7 —
> Unique local addresses)
>
> [Oh wow, that subject field, so handy to indicate a topic change! ;) ]
>
> Short answer: you announce both PA prefixes using Router Advertisement
> (RA) inside the network. You pull the RA when a uplink goes
> down/breaks.

That assumes importing some sort of routing state into your RA config.  Sort of a conditional RA.  Can that be done 
today by anyone?

> Sessions break indeed, but because there is the other prefix they fall
> over to that and build up new sessions from there.

This still doesn’t address breakage that happens AFTER your link to your upstream.  What if your upstream has a peering 
issue or their peer has a peering issue?  How do you detect that the distant end has a route back to that prefix but 
doesn't to the other?  You can't.