Users Guide

MAC ACLs. You can congure 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 ow-based monitoring for a monitoring session by entering the flow-based enable
command in the Monitor Session mode. When you enable this capability, trac with particular ows 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
specied trac instead all trac on the interface. This feature is particularly useful when looking for
malicious trac. It is available for Layer 2 and Layer 3 ingress and egress trac. You may specify trac 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
ip access-list extended — creates an extended ACL.
permit — assigns a permit lter for IP packets.
permit tcp — assigns a permit lter for TCP packets.
permit (for Extended IP ACLs)
To pass IP packets meeting the lter criteria, congure a lter.
Syntax
permit {source mask | any | host ip-address} {destination mask | any | host
ip-address} [count [bytes]] [dscp value] [order] [fragments] [log [interval
minutes] [threshold-in-msgs [count]] [monitor]
To remove this lter, you have two choices:
• Use the no seq sequence-number command if you know the lter’s sequence number.
•
Use the no deny {source mask | any | host ip-address} {destination mask |
any | host ip-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. 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 interval range is from 1 to 10 minutes.
monitor (OPTIONAL) Enter the keyword monitor when the rule is describing the trac
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 ve minutes. By default, ow-based monitoring is
not enabled.
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Access Control Lists (ACL)