Anycast DNS - anybody?

Ashish Shukla आशीष शुक्ल at
Fri Jan 18 13:40:37 PST 2008

>>>>> Regarding Anycast DNS - anybody?; Ewald Jenisch <a at> adds:
    Ewald> Hi,

    Ewald> Has anybody out there configured anycast DNS (where multiple instances
    Ewald> of a DNS-server run under the same IP-address in different parts of
    Ewald> the network) under FreeBSD?

AFAIK, anycast requires magic at routing level. So that user will
connect to the nearest DNS server (holding the anycast address).

    Ewald> I'm looking for some hints to get started, but googling around didn't
    Ewald> provide much info on that topic...

It has do with routing so you need to investigate on routing
protocols, like RIP, etc.        network
 [server1] --- [router1]  =================    [router2] ---  [server2]

router1, router2 -- redundant routers connecting to different ISPs

So if router2 receives packet destined for, instead of sending to
server1 it'll send it to server2, since server2 is nearest to it, and
vice versa. Above is a very simple configuration describing anycast.

Since Anycast works only for connection-less protocols, you don't need
to keep TCP connections synchronized between two servers, although both servers
should behave identically, i.e. return similar records.

BtW, I've never implemented anycast ever, so its fully based on my imagination.

Ashish Shukla आशीष शुक्ल            
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