IPv4 Access Control Lists (ACLs)

Enable ACL “Deny” Logging

ACL Logging Operation

When the switch detects a packet match with an ACE and the ACE includes both the deny action and the optional log parameter, an ACL log message is sent to the designated debug destination. The first time a packet matches an ACE with deny and log configured, the message is sent immediately to the destination and the switch starts a wait-period of approximately five minutes. (The exact duration of the period depends on how the packets are internally routed.) At the end of the collection period, the switch sends a single-line summary of any additional “deny” matches for that ACE (and any other “deny” ACEs for which the switch detected a match). If no further log messages are generated in the wait-period, the switch suspends the timer and resets itself to send a message as soon as a new “deny” match occurs. The data in the message includes the information illustrated in figure 9-33.

Feb 1 10:04:45 10.10.20.1 ACL:

ACL 02/01/07 10:04:45 List NO-TELNET, seq#10 denied tcp 10.10.10.3(1612)->10.10.20.2(23) on vlan 1, port A7

Feb 1 10:04:45 10.10.20.1 ACL:

ACL 02/01/07 10:04:45 : ACL NO-TELNET seq#10 denied 6 packets

Example Syslog report of the first deny event detected by the switch for this ACE.

Example of subsequent deny events detected by the switch for the same ACE.

Figure 9-33. Content of a Message Generated by an ACL-Deny Action

9-97