Logging for a specific ACL line

marcos.sousa7 — Tue, 12 Mar 2019 05:32:02 GMT

Hello, I'm currently evaluating rules on ASA.

There are some rules applied, but some of the traffic does not match those rules. I created a rule allowing everything and I need to see what traffic is hitting this especific rule on line 3.

Example:
access-list OUTSIDE_IN line 1 extended permit tcp 10.1.16.0 255.255.255.0 10.153.224.0 255.255.240.0 eq 88
access-list OUTSIDE_IN line 2 extended permit udp 10.1.16.0 255.255.255.0 10.153.224.0 255.255.240.0 eq domain
access-list OUTSIDE_IN line 3 extended permit ip 10.1.16.0 255.255.255.0 10.153.224.0 255.255.240.0 log informational

When I enable log, I see all the traffic, not the only one I wanted. There's a way to see only traffic coming on line 3?

Regards

Hi Marcos,

Milan Mesic — Sun, 22 Feb 2015 18:12:53 GMT

Hi Marcos,

You see all traffic because for lines for which no "log" keyword at ACL line end is added, it will still be logged, see:

http://www.cisco.com/c/en/us/td/docs/security/asa/asa81/command/ref/refgd/a1.html#wp1564948

... If you enter the log keyword without any arguments, you enable system log message 106100 at the default level (6) and for the default interval (300 seconds). If you do not enter the log keyword, then the default system log message 106023 is generated...

So what you can do is instead of "log informatioanl", put "log warnings" to log this ACL line 3 at syslog level 4 (warnings), and in addition to that decrease logging level that is visible for the method how you monitor logs, for example some of following lines (depending whether you monitor logs at syslog server, terminal, or from local buffer (show logg command):

hostname(config)# logging trap warnings

hostname(config)# logging enable

hostname(config)# logging monitor warnings

hostname(config)# terminal monitor

hostname(config)# logging buffered warnings

Also, before any significant changes to ASA configuration, migrations, software upgrades, etc., I always recommend testing the configuration with fw123test:

http://www.networksea.com/fw123test/

BR,

Milan

topic Logging for a specific ACL line in Network Security

Logging for a specific ACL line

Hi Marcos,