FQDN not working vs Resolved IP address

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L1 Bithead

FQDN not working vs Resolved IP address

I created a new FQDN address object to facilitate a new Policy(rule).

 When tested the FQDN resolves internal to the Palo Alto Firewall.

The rule contains one destination address which is the new company.fqdn.com FQDN

The rule contains one source address

Application SSL with Application-Default Service

Action Allow

 

When attempts are made to connect  to this destination via the new rule with the FQDN set(destination), the traffic is denied(fails) and logs point to(identify) the "interzone-default" rule instead of the "new rule" that is set up to facilitate this connection 

 

But when I replace the FQDN(destination) with it's resolved IP in the new rule, it works fine(allowed) and logs point the occurrence to the "new rule" (not the interzone-default) as to be expected since that is normal behavior 

Questions:

  1. Why would the interzone-default rule become a part of the failed attempt to connect to the new rule
  2. Anyone know why connection fails with the FQDN set as destination rather than it's resolved IP address
  3. As anyone had a similar experience

Thanks in advance.


Accepted Solutions
Highlighted
Cyber Elite

Re: FQDN not working vs Resolved IP address

@rockfort 

Questions:

1. Why would the interzone-default rule become a part of the failed attempt to connect to the new rule

Because the new rule isn't properly matching the traffic. I would verify with the 'request system fqdn show' or ''show dns-proxy fqdn all' depending on your currently installed version of PAN-OS to verify that the firewall is actually properly resolving the FQDN object to the proper address.

 

2. Anyone know why connection fails with the FQDN set as destination rather than it's resolved IP address

99.8% of the time, this is due to the FQDN object either not refreshing properly or the rule not properly being built to accommodate for the traffic that's actually being seen by the firewall. Once you've verified the FQDN object is resolving properly, you'll want to test the rulebase entry and look at the recorded logs and make sure that your rulebase entry as configured properly accounts for the traffic. 

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Highlighted
Cyber Elite

Re: FQDN not working vs Resolved IP address

@rockfort 

Questions:

1. Why would the interzone-default rule become a part of the failed attempt to connect to the new rule

Because the new rule isn't properly matching the traffic. I would verify with the 'request system fqdn show' or ''show dns-proxy fqdn all' depending on your currently installed version of PAN-OS to verify that the firewall is actually properly resolving the FQDN object to the proper address.

 

2. Anyone know why connection fails with the FQDN set as destination rather than it's resolved IP address

99.8% of the time, this is due to the FQDN object either not refreshing properly or the rule not properly being built to accommodate for the traffic that's actually being seen by the firewall. Once you've verified the FQDN object is resolving properly, you'll want to test the rulebase entry and look at the recorded logs and make sure that your rulebase entry as configured properly accounts for the traffic. 

View solution in original post

Highlighted
L1 Bithead

Re: FQDN not working vs Resolved IP address

Thank you very much

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