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 ip access-list extended — creates an extended ACL.
permit — assigns a permit filter for IP packets.
permit tcp — assigns a permit filter for TCP packets.
permit (for Extended IP ACLs)To pass IP packets meeting the filter criteria, configure a filter.
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 filter, you have two choices:
• Use the no seq sequence-number command if you know the filter’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 traffic that you want to monitor and the ACL
in which you are creating the rule is applied to the monitored
interface.
290 Access Control Lists (ACL)