Intradomain DNS Anycast revisited

Sun Mar 27 16:44:34 UTC 2005

On Mar 26, 2005, at 1:41 PM, just me wrote:
>   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?
>

configure a loopback interface on your dns servers and advertise a 
route to that loopback address to your connected routers... Why the 
hell do you want to use static routes when you don't need to... Yuck

>   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 ?

Servers a cheaper than good routers... Why don't you just have your dns 
server connected to one router.... If you want dns servers on multiple 
subnets, spend a couple of grand and get a cheap 1U dell server for 
your other rack... Why do you need to worry about default routes? You 
are running a dynamic routing protocol on your dns server. Anycast dns 
pretty much relies on ospf working... Hell, you don't need any default 
gateway on your host... Let you quagga worry about routing...

Set up your ospf area as an nssa.... Your dns server only needs to 
LEARN default from the connected routers... You will be doing a 7-5 
conversion on your asbrs.

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

What does bind care? We are talking unicast... If the packet can get to 
your dns server, bind can probably get the answer back. You are making 
this much more difficult than it needs to be....

http://www.net.cmu.edu/pres/anycast

Check out this presentation....

Peter

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