Intradomain DNS Anycast revisited

just me matt at snark.net
Sat Mar 26 21:41:24 UTC 2005



It has been my experience in the deployment of such anycasted dns 
server pods that pushing ospf from the dns server hosts introduces 
complexity and reduces reliability to the point that other, simpler 
solutions become much more attractive.

You should also take a moment to take a look at your spanning tree 
configuration, depending on how you care configuring your switches.

matto


On Fri, 25 Mar 2005, Joe Shen wrote:
  
  I'm trying to set up a anycast DNS server farm for
  customer service. In order to improve availability, we
  plan to install those servers in
  one LAN which has the similar structure like :
  
  
  server-(1,3)---switch1---router-1---(outside)
                   |
                   |
  server-(2,4)---switch2---router-2---(outside)
  
  
  The four unix servers are all unix boxes, switch-1 &
  switch-2 are interconnected to guarantee the
  availability. BIND is to be used as
  DNS cache server software, Quagga OSPFD is used to be
  routing software.
  
  According to above configuration, both routers will
  know multiple paths to dns cache server, while dns
  cache server should know two
  paths to outside network. Here comes my questions:
  
  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?
  
  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 ?
  
  3) Is there any requirement on BIND to fit to such
  multipath routing situation?
  
  Joe
  
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--matt at snark.net------------------------------------------<darwin><
              The only thing necessary for the triumph
              of evil is for good men to do nothing. - Edmund Burke



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