Hi Filip,
I looked up these syslog messages. The first one (710005) makes sense:
Explanation The ASA does not have a UDP server that services the UDP request. Also, a TCP packet that does not belong to any session on the ASA may have been discarded.
There is no DNS server on the ASA so it discards these DNS packets.
The second (331002) shows that the ASA does register something locally:
Explanation A dynamic DNS update succeeded in the DNS server.
And the last one (331001) shows that it was unable to register something with the DNS server.
Explanation: The dynamic DNS subsystem failed to update the resource records on the DNS server. This failure might occur if the ASA is unable to contact the DNS server or the DNS service is not running on the destination system.
I’m guessing you can reach the pi-hole DNS server from your ASA?
I’m not exactly sure what the ASA did when it shows syslog 331002. Does this show up when the device just got an IP address?
Do you have any of the DDNS settings configured on your ASA?
You configure the DDNS update settings for the DHCP server in the Dynamic DNS Settings for DHCP Server area. Check the Update DNS Clients check box to specify that, in addition to the default action of updating the client PTR resource records, the selected DHCP server should also perform the following update actions:
Check the Update Both Records check box to specify that the DHCP server should update both the A and PTR RRs.
Check the Override Client Settings check box to specify that the DHCP server actions should override any update actions requested by the DHCP client.
This might be a way to get those device records in your pihole DNS server. I haven’t tried this before though.
Rene