Reference Guide
Figure 100. Port Monitoring Configurations on the S-Series
FTOS Behavior: All monitored frames are tagged if the configured monitoring direction is transmit (TX), regardless of
whether the monitored port (MD) is a Layer 2 or Layer 3 port. If the MD port is a Layer 2 port, the frames are tagged with
the VLAN ID of the VLAN to which the MD belongs. If the MD port is a Layer 3 port, the frames are tagged with VLAN ID
4095. If the MD port is in a Layer 3 VLAN, the frames are tagged with the respective Layer 3 VLAN ID. For example, in the
configuration source gig 6/0 destination gig 6/1 direction tx, if the MD port gigabitethernet 6/0 is an untagged member of
any VLAN, all monitored frames that the MG port gigabitethernet 6/1 receives are tagged with the VLAN ID of the MD
port. Similarly, if BPDUs are transmitted, the MG port receives them tagged with the VLAN ID 4095. This behavior might
result in a difference between the number of egress packets on the MD port and monitored packets on the MG port.
FTOS Behavior: The S4820T continues to mirror outgoing traffic even after an MD participating in spanning tree protocol
(STP) transitions from the forwarding to blocking.
Configuring Port Monitoring
To configure port monitoring, use the following commands.
1. Verify that the intended monitoring port has no configuration other than no shutdown, as shown in the following
example.
EXEC Privilege mode
show interface
2. Create a monitoring session, as shown in the following example.
CONFIGURATION mode
monitor session
3. Specify the source and destination port and direction of traffic, as shown in the following example.
MONITOR SESSION mode
source
To display monitor sessions, use the show monitor session command in EXEC Privilege mode.
Example of Viewing Port Monitoring Configuration
FTOS(conf-if-gi-1/2)#show config
!
interface GigabitEthernet 1/2
no ip address
no shutdown
FTOS(conf-if-gi-1/2)#exit
FTOS(conf)#
monitor session 0
FTOS(conf-mon-sess-0)#source gig 1/1 dest gig 1/2 direction rx
FTOS(conf-mon-sess-0)#exit
FTOS(conf)#do show monitor session 0
SessionID Source Destination Direction Mode Type
619