transparent DNS load-balancing with a Cisco ACE

John Miller johnmill at brandeis.edu
Fri Oct 19 18:25:13 UTC 2012


Hello everyone,

Perhaps a Cisco list is a better destination for this, but I've seen a 
similar post here in the past couple of months, so posting here as well.

I'm trying to get our Cisco ACE set up appropriately to handle DNS 
traffic.  So far, I've gotten it working using NAT (each rserver has a 
public and a private IP) and using transparent load-balancing (ACE talks 
directly to the public IP), aka direct server return.

Here's a question, however: how does one get probes working for a 
transparent LB setup?  If an rserver listens for connections on all 
interfaces, then probes work fine, but return traffic from the uses the 
machine's default IP (not the VIP that was originally queried) for the 
source address of the return traffic.

What have people done to get probes working with transparent LB?  Are 
any of you using NAT to handle your dns traffic?  Not tying up NAT 
tables seems like the way to go, but lack of probes is a deal-breaker on 
this end.

-- 
John Miller
Systems Engineer
Brandeis University
johnmill at brandeis.edu



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