Forum Discussion

sameh_atef_2110's avatar
sameh_atef_2110
Icon for Cirrus rankCirrus
Jan 21, 2019

Local Pool of DNS under Listener not working as expected

We are configuring the GTM to be working as a proxy. So, in case there is no Wide IP is being matched by the DNS query it should forward the DNS query to a local pool of DNS Servers. I have configured the local pool of dns servers and associated it under the listener as the as the default pool. However, the requests are coming to the listener but maybe not forwarded to the DNS servers. I can see from statistics on GTM that there are IN packets coming to listener and Pool but there are no OUT packets.

 

Any idea why is this happening ?!

 

I have verified the connectivity between listener and DNS servers and they are on the same subnet.

 

application delivery
BIG-IP
BIG-IP DNS
  • youssef1's avatar
    youssef1
    Icon for Cumulonimbus rankCumulonimbus
    Jan 21, 2019

    Hi,

     

    I supose that you set a DNS profile.

     

    Can you validate that in this DNS profile you set the setting "Unhandled Query Actions" to "allow":

     

    Allow: The BIG-IP system forwards queries to a DNS server or pool member. If a pool is not associated with a listener and the Use BIND Server on BIG-IP setting is set to Enabled, requests are forwarded to the local BIND server.

     

    regards

     

  • Kai_Wilke's avatar
    Kai_Wilke
    Icon for MVP rankMVP
    Jan 22, 2019

    Hi Sameh,

    could be a asymetric routing issue?

    Depending on your network configuration you may have to enable 

    snat automap
    on the VS to allow the DNS server to route packets back to your F5.

    If this does not work out, then make sure the DNS server is receiving the DNS request (e.g pcap on your DNS servers)

    Cheers, Kai