ASA NAT Bug

CSCun95075 - ASA drops packet due to nat-no-xlate-to-pat-pool after removing NAT rule

 

Symptom:
Once a twice NAT rule with a service translation is added, other traffic on the interface may also be dropped with a reason of nat-no-xlate-to-pat-pool. This is expected behavior and more details can be found here:

http://www.cisco.com/c/en/us/td/docs/security/asa/asa91/configuration/firewall/asa_91_firewall_config/access_fwaaa.html#wp1331733

However, if the NAT rule references an object-group and that object-group is changed while the NAT rule is still configured, traffic may still be dropped even after removing the NAT rule.

Conditions:
All of the following conditions must be matched to see this issue:

1) The ASA is configured with a twice NAT rule that uses a service translation
2) The object-group referenced in the NAT rule is edited (i.e. a new network-object is added to it) while the NAT rule is still configured
3) The NAT rule is removed from the configuration

Workaround:
Reloading the ASA after the offending NAT rule is removed will resolve the issue.

 

Bug Fixed in release : 9.1.5(1) or 9.1.2(100)

Regards

Karthik