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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
permit — configures a MAC address filter to pass packets.
seq — configures a MAC address filter with a specified sequence number.
deny (for Extended MAC ACLs)
To drop packets that match the filter criteria, configure a filter.
Syntax
deny {any | host mac-address | mac-source-address mac-source-
address-mask} {any | host mac-address | mac-destination-address
mac-destination-address-mask} [ethertype-operator] [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 if you know the filter’s
sequence number.
• Use the no deny {any | host mac-address | mac-source-address
mac-source-address-mask} {any | host mac-address | mac-
destination-address mac-destination-address-mask} 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 time interval range is from 1 to 10 minutes.
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Access Control Lists (ACL)