* Chris Adams
This brings up something else I'm trying to figure out. We're not a huge ISP; I've got our /32 but I don't see us using more. We have two main POPs, each with Internet links, plus a link between the two. Our IPv4 allocations are larger than the minimum, so I split our IPv4 space between the two POPs and avertise a smaller block out of the smaller of the two POPs.
This has worked okay and handles the POP-to-POP link going down; when that happens, our POP-to-POP traffic (not a large precentage of our traffic) goes across our Internet connections, but Internet traffic for each POP goes to directly to the POP.
With IPv6, we've got our single /32. From what I understand, if I try to advertise a /33 from the smaller POP, many (most?) will drop it (if my upstreams even take it). If I advertise the /32 from both routers, when that link goes down, my IPv6 traffic will be pretty much hosed.
What you can do is to set up a tunnel between the sites (can be encrypted if necessary) through your upstream(s), and include it in your IGP - making sure that it has a higher cost/metric than the dedicated circuit. If then the dedicated circuit goes down, the traffic between the PoPs is redirected through the tunnel, and no connectivity is lost. You might need to upgrade the capacity of the dedicated circuit though, since there's no avoiding that some inbound packets will be delivered to the wrong PoP. Also you should make sure that the ports to your upstreams have enough available burst capacity (and preferably a roomy percentile-based charging scheme so that a bit of downtime on the dedicated circuit won't cost you anything). If you're single-homing to the the same upstream AS at both sites, another solution is to announce the aggregate /32 from both PoPs and at the same time a more specific route from each of them tagged with the no-export community (assuming your upstream will accept the deaggregated route in both locations). Best regards, -- Tore Anderson Redpill Linpro AS - http://www.redpill-linpro.com/ Tel: +47 21 54 41 27