Reference Guide

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Port Monitoring
Port monitoring is supported on the S4820T platform.
Port monitoring is a feature that 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). Port
monitoring functionality is different between platforms, but the behavior is the same, with highlighted exceptions.
Important Points to Remember
• Port monitoring is supported on physical ports only; virtual local area network (VLAN) and port-channel
interfaces do not support port monitoring.
• A synchronous optical network technologies (SONET) port may only be a monitored port.
• The monitored (the source, [MD]) and monitoring ports (the destination, [MG]) must be on the same switch.
• In general, a monitoring port should have no ip address and no shutdown as the only configuration; FTOS
permits a limited set of commands for monitoring ports. You can display these commands using the ? command.
A monitoring port also may not be a member of a VLAN.
• There may only be one destination port in a monitoring session.
• Only one destination port (MG) can monitor a source port (MD). If you try to assign a monitored port to more than
one monitoring port, the following message displays:
FTOS(conf)#mon ses 1
FTOS(conf-mon-sess-1)#$gig 0/0 destination gig 0/60 direction both
FTOS(conf-mon-sess-1)#do show mon ses
SessionID Source Destination Direction Mode Type
--------- ------ ----------- --------- ---- ----
1 Gi 0/0 Gi 0/60 both interface Port-based
FTOS(conf-mon-sess-1)#mon ses 2
FTOS(conf-mon-sess-2)#source gig 0/0 destination gig 0/61 direction both
% Error: MD port is already being monitored.
• The maximum number of monitoring sessions is two per system. The maximum sessions are ∞.
• If each port monitoring session has a unique destination port, up to two port monitoring sessions are supported.
If the destination port is the same, up to four port monitoring sessions are supported.
Port Monitoring
The S4820T supports multiple source-destination statements in a monitor session.
There may only be one destination port in a monitoring session (% Error: Only one MG port is allowed
in a session.
).
The number of source ports FTOS allows within a port-pipe is equal to the number of physical ports in the port-pipe (n).
However, n number of ports may only have four different destination ports.
In the following examples, ports 0/13, 0/14, 0/15, and 0/16 all belong to the same port-pipe. They are pointing to four
different destinations (0/1, 0/2, 0/3, and 0/37). Now it is not possible for another source port from the same port-pipe (for
example, 0/17) to point to another new destination (for example, 0/4). If you attempt to configure another destination, this
message displays: % Error: Exceeding max MG ports for this MD port pipe.
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