Users Guide

Usage Information
When the configured maximum threshold is exceeded, generation of logs is stopped.
When the interval at which ACL logs are configured to be recorded expires, the
subsequent, fresh interval timer is started and the packet count for that new interval
commences from zero. If ACL logging was stopped previously because the configured
threshold is exceeded, it is re-enabled for this new interval.
If ACL logging is stopped because the configured threshold is exceeded, it is re-
enabled after the logging interval period elapses. ACL logging is supported for standard
and extended IPv4 ACLs, IPv6 ACLs, and MAC ACLs. You can configure ACL logging
only on ACLs that are applied to ingress interfaces; you cannot enable logging for ACLs
that are associated with egress interfaces.
You can activate flow-based monitoring for a monitoring session by entering the flow-
based enable command in the Monitor Session mode. When you enable this capability,
traffic with particular flows that are traversing through the ingress and egress interfaces
are examined and, appropriate ACLs can be applied in both the ingress and egress
direction. Flow-based monitoring conserves bandwidth by monitoring only specified
traffic instead all traffic on the interface. This feature is particularly useful when looking
for malicious traffic. It is available for Layer 2 and Layer 3 ingress and egress traffic. You
may specify traffic using standard or extended access-lists. This mechanism copies all
incoming or outgoing packets on one port and forwards (mirrors) them to another
port. The source port is the monitored port (MD) and the destination port is the
monitoring port (MG).
Related
Commands
• deny tcp — assign a filter to deny TCP packets.
• deny udp — assign a filter to deny UDP packets.
• ip access-list extended — create an extended ACL.
seq (for Standard IPv4 ACLs)
Assign a sequence number to a deny or permit filter in an IP access list while creating the filter.
Syntax
seq sequence-number {deny | permit} {source [mask] | any | host
ip-address}} [count [bytes]] [dscp value] [order] [fragments] [log
[interval minutes] [threshold-in-msgs [count]] [monitor]
To delete a filter, use the no seq sequence-number command.
Parameters
log (OPTIONAL) Enter the keyword log to enable the triggering of
ACL log messages.
threshold-in msgs
count
(OPTIONAL) Enter the threshold-in-msgs keyword followed
by a value to indicate the maximum number of ACL logs that
can be generated, exceeding which the generation of ACL logs
Access Control Lists (ACL) 350