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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 (for IPv6 ACLs)
Configure a filter that drops IPv6 packets that match the filter criteria.
Syntax
deny {ipv6-protocol-number | icmp | ipv6 | tcp | udp} [count [byte]]
[dscp value] [order] [fragments] [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 {ipv6-protocol-number | icmp | ipv6 | tcp | udp} command
Parameters
count OPTIONAL) Enter the keyword count to count packets processed by the filter.
byte (OPTIONAL) Enter the keyword byte to count bytes processed by the filter.
dscp (OPTIONAL) Enter the keyword dscp to match to the IP DSCP values.
order (OPTIONAL) Enter the keyword order to specify the QoS order of priority for the
ACL entry. The range is from 0 to 254 (where 0 is the highest priority and 254
is the lowest; lower order numbers have a higher priority). If you do not use the
order keyword, the ACLs have the lowest order by default as 255.
fragments Enter the keyword fragments to use ACLs to control packet fragments.
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. The threshold range is from 1 to 100.
interval minutes (OPTIONAL) Enter the keyword interval followed by the time period in minutes
at which ACL logs must be generated. The time interval range is from 1 to 10
minutes.
monitor (OPTIONAL) Enter the keyword monitor when the rule is describing the traffic
that you want to monitor and the ACL in which you are creating the rule is applied
to the monitored interface.
Defaults By default, 10 ACL logs are generated if you do not specify the threshold explicitly. The default frequency
at which ACL logs are generated is five minutes. By default, flow-based monitoring is not enabled.
Command Modes ACCESS-LIST
Supported Modes Full–Switch
Command
History
Version Description
9.9(0.0) Introduced on the FN IOM.
Access Control Lists (ACL) 239