Intradomain DNS Anycast revisited

Fri Mar 25 07:19:06 UTC 2005

thanks.

> 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... 

Do you mean Quagga's OSPF route has higher priority
than static route?  or even there is static default
route configured, once Quagga detects link to default
router is down it will replace  0.0.0.0/0.0.0.0  in
host routing table?

>     > 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.
>

I don't understand why should both routers be iBGP
peers.  In fact, iBGP does not run on that two
routers; the two routers are only members of  OSPF
backbone area who only run OSPF; only  border router (
at the edge of our network) runs BGP and enject
default route into OSPF backbone area. 

Although all DNS servers are cache server, we have to
open 53/TCP to allow resolver using TCP protocol. For
example,

server-(1,3)--switch--router-1--\
                | (OSPF only)  router3--host
server-(2,4)--switch--router-2--/

if that possible that router3 or router-1 dispers
packets of the same TCP connection to different path? 
Is there possibility that a DNS requests are divided
into multiple UDP packets?

>     > 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.
> 

Do I only need to configure BIND to origin request
from administration IP address ( configured on NIC and
different from DNS service address)?

regards

Joe 

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