Administrator Guide

The default frequency at which ACL logs are generated is five minutes. By default, flow-based monitoring is not
enabled.
Command Modes ACCESS-LIST
Command History
Version Description
9.9(0.0) Introduced on the C9010.
9.5(0.1) Introduced on the Z9500.
9.4(0.0) Added support for flow-based monitoring on the S4810, S4820T, S6000, and Z9000
platforms.
9.3(0.0) Added support for logging of ACLs on the S4810, S4820T, and Z9000 platforms.
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).
deny icmp (for Extended IPv6 ACLs)
Configure a filter to drop all or specific ICMP messages.
C9000 Series
NOTE:
Only the options that have been newly introduced in Release 9.3(0.0) and Release 9.4(0.0) are described here.
For a complete description on all of the keywords and variables that are available with this command, refer the topic of
this command discussed earlier in this guide.
Syntax
deny icmp {source address mask | any | host ipv6-address} {destination address
| any | host ipv6-address} [message-type] [count [byte]] | [log [interval
minutes] [threshold-in-msgs [count]] [monitor]
To remove this filter, you have two choices:
• Use the no seq sequence-number command syntax if you know the filter’s sequence number
• Use the no deny icmp {source address mask | any | host ipv6-address}
{destination address | any | host ipv6-address} 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 is terminated. with the seq, permit, or deny commands. You can enter a
threshold in the range of 1-100.
interval minutes (OPTIONAL) Enter the keyword interval followed by the time period in minutes at
which ACL logs must be generated. You can enter an interval in the range of 1-10 minutes.
906 IPv6 Access Control Lists (IPv6 ACLs)