Hello community,
inside of our network we use DNS forwardes pointed to Cisco Umbrella DNS servers.
Software using these forwarders is generating events about failed PTR DNS lookups with string "DNS temporarily down".
Connection to outside is managed by Cisco ASA, gathering the packets I have found just general errors:
Flags: 0x8182 Standard query response, Server failure
error: .... .... .... 0010 = Reply code: Server failure (2)
I have noticed that actually none of these IPs has functional PTR. Mostly these IPs are listed on spam servers.
So to me it looks that the server is actually not able to verify there is no PTR.
On the other end many of such PTR requests are successful.
Example of IP and error from the server:
DNS error. Cannot do PTR look up on <137.220.234.110>. DNS temporarily down
Do you have any idea what could be causing this issue?
Thank you!
