Users Guide

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
• ip access-list extended — create an extended ACL.
• permit — assign a permit filter for IP packets.
• permit tcp — assign 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
Access Control Lists (ACL) 373