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Craig_13881's avatar
Craig_13881
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Jul 25, 2011

Return DNS replies to specific clients

I'm trying to return DNS replies to only a couple of different subnets. If the request comes in from anything else, I'd like to ignore it, or return a bogus response. Trying to get this to work, but...
application delivery
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devops
iRules
Craig_13881's avatar
Craig_13881
Icon for Nimbostratus rankNimbostratus
Jul 26, 2011
That looks perfect, but when I test it out, I get www.blahblahblah.com even though the source IP in the packet capture is in the 192.168.76.0/24 range. I should mention that I'm testing this from my workstation, which is asking a Microsoft DNS server, and that DNS server is handing the request off to the GTM. I can see blahblahblah showing up in a Wireshark trace on my PC and I've verify the source IP that hitting the GTM with a TCPdump. I may try just putting the IP address of the DNS server in the iRule as a host entry instead of a subnet and see if I can get it to work. It's like the "if" condition is coming up "true" when it should evaluate to "false".

Here's what I have I added a subnet and a closing brace at the end. (The GTM was barking at me about the closing brace.) 

when DNS_REQUEST {
  if { !([IP::addr [IP::client_addr]/24 equals 10.0.0.0/24]) or !([IP::addr [IP::client_addr]/24 equals 192.168.76.0/24]) or !([IP::addr [IP::client_addr]/24 equals 172.16.1.0/24]) } {
   cname www.blahblahblah.com
     }
}