CLI Reference Guide-R04

Chapter 13 | Port Mirroring Commands
Local Port Mirroring Commands
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Default Setting
◆ No mirror session is defined.
◆ When enabled for an interface, default mirroring is for both received and
transmitted packets.
◆ When enabled for a VLAN or a MAC address, mirroring is restricted to received
packets.
Command Mode
Interface Configuration (Ethernet, destination port)
Command Usage
◆ You can mirror traffic from any source port to a destination port for real-time
analysis. You can then attach a logic analyzer or RMON probe to the destination
port and study the traffic crossing the source port in a completely unobtrusive
manner.
◆ Set the destination port by specifying an Ethernet interface with the interface
configuration command, and then use the port monitor command to specify
the source of the traffic to mirror. Note that the destination port cannot be a
trunk or trunk member port.
◆ When mirroring traffic from a port, the mirror port and monitor port speeds
should match, otherwise traffic may be dropped from the monitor port. When
mirroring traffic from a VLAN, traffic may also be dropped under heavy loads.
◆ Spanning Tree BPDU packets are not mirrored to the target port.
◆ You can create multiple mirror sessions, but all sessions must share the same
destination port.
◆ The destination port cannot be a trunk or trunk member port.
Example
The following example configures the switch to mirror all packets from port 6 to 5:
Console(config)#interface ethernet 1/5
Console(config-if)#port monitor ethernet 1/6 both
Console(config-if)#