dns lookup Cisco ASA

[giuseppe parlato]

Hi,

dnslookp on Cisca ASA works :

fw-asa/pri/act# ping imap.gmail.com
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 173.194.67.109, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/28/30 ms

object network obj-imap.gmail.com
 fqdn v4 imap.gmail.com

access-list ACL_APP extended permit tcp host 192.168.100.81 object obj-imap.gmail.com eq 993

WHY acl above have hit=0 ? acl works I'm sure cause if I disable it then 192.168.100.81 cannot connect to imap.gmail.com

ALSO on syslog server searching for destination fqdn there is no entry

[Karsten Iwen · Accepted solution]

The FQDN-object is only used to populate the ACL with ACEs that have the corresponding IP(s) as the destination. These Lines have the relevant hitcounts. On the log, you also have to search for the real IP which would be 173.194.67.109 in your example.

[giuseppe parlato]

Thanks for your answer.

I'm facing some problems anyway, I have two firewalls and same dns server,

the first one ASA:

fw-asa1/pri/act# sh dns host pop.gmail.com
Name: pop.gmail.com
  Address: 173.194.66.109                                TTL 11:35:28
  Address: 173.194.66.108                                TTL 11:35:28
  Address: 173.194.78.108                                TTL 03:48:47
  Address: 173.194.78.109                                TTL 03:48:47

..while the second one ASA:

fw-asa2/pri/act# sh dns host pop.gmail.com
Name: pop.gmail.com
  Address: 173.194.66.109                                TTL 11:35:34
  Address: 173.194.66.108                                TTL 11:35:34
  Address: 173.194.78.108                                TTL 10:44:28
  Address: 173.194.78.109                                TTL 10:44:28
  Address: 173.194.67.109                                TTL 10:49:28
  Address: 173.194.67.108                                TTL 10:49:28

I cant understand the reason why they have different entries. Sometimes something is missing so traffic to pop.gmail.com is blocked. Server which has to connect by pop to gmail pop server is targeting pop.gmail.com resolving it through the same dns server used by ASA. Do I have to work with timers (I've changed expire timeout to 12 hours but there are still some missed entries sometimes)? Don't really know.