ISP customer assignments

Tore Anderson tore at linpro.no
Fri Oct 16 12:02:21 UTC 2009


* 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




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