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Re: Intradomain DNS Anycast revisited

  • From: Bill Woodcock
  • Date: Fri Mar 25 01:27:31 2005

    > 1) should each dns cache server be configured a static
    > default route (0.0.0.0/0.0.0.0)? If server-(1,3) is
    > configured statically to use
    > router-1 as default router, will Quagga make it use
    > router-2 when router-1 is not reachable?

No, because both routers are reached through the same L1/L2 medium, so 
Quagga can't use link-state to determine reachability of the next-hop.
You could fix that by getting rid of the switches, and just having a bunch 
of router interfaces facing two Ethernet interfaces on each server, which 
would remove some points of failure, and would be a good idea if you can 
spare the router interfaces...   or you could use the OSPF which you're 
already going to be running, to advertise a default from both routers to 
each of the servers.

    > 2) If each server is configured two default router (
    > router-1 &
    > router-2), or each server learn route 0.0.0.0/0.0.0.0
    > by OSPF ( our border router inject default route into
    > OSPF ); there should be
    > two equal cost path to 0.0.0.0/0.0.0.0 on each DNS
    > server, the DNS server should disperse any outgoing
    > packets onto the two paths, will
    > that do harm to  DNS service ?
    
Nope, no problem, particularly so long as the two routers are iBGP peers, 
so they'll both (for the most part) have the same idea of what selected 
paths are.

    > 3) Is there any requirement on BIND to fit to such
    > multipath routing situation?

Nope.  BIND doesn't know what's going on that far below it.

                                -Bill





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