deploying DNS in large ISP

[Barry Margolin]

We're using an "anycasting" mechanism for our caching DNS servers.  We've
deployed servers in most of our large POPs, and configured them with
virtual addresses corresponding to the resolver addresses that we tell our
customers to use (we sell leased-line services, not dialup, so we don't do
DHCP for our customers).  These addresses are redistributed into our OSPF
routing process, so our backbone automatically routes DNS lookups to the
closest caching server.

We're currently using static routes on the upstream routers, so removing a
server requires manual configuration changes by our network operators.  It
would probably be better to run gated on the server so that it would
advertise itself, and the advertisement would go away automatically if the
server crashes.  But when we set this up we decided to go the simple route
(no pun intended).  Even if we ran gated, we'd need to be able to disable
the route if the system stayed up but named died.

-- 
Barry Margolin, barmar at genuity.net
Genuity, Burlington, MA
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