Reference Guide
Port Monitoring | 691
Figure 32-4. Number of Monitoring Ports on the C-Series and S-Series
A source port may only be monitored by one destination port (Message 6), but a destination port may
monitor more than one source port. Given these parameters, Figure 32-1 illustrates conceptually the
possible port monitoring configurations on the C-Series and S-Series.
Figure 32-5. Port Monitoring Configurations on the C-Series and S-Series
Message 5 One Destination Port in a Monitoring Session Error Message on C-Series and S-Series
% Error: Exceeding max MG ports for this MD port pipe.
Message 6 One Destination Port per Source Port Error Message
% Error: MD port is already being monitored.
FTOS Behavior: On the C-Series, S-Series and Z-Series, 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(conf-mon-sess-300)#do show mon session
SessionID Source Destination Direction Mode Type
--------- ------ ----------- --------- ---- ----
0 Gi 0/13 Gi 0/1 rx interface Port-based
10 Gi 0/14 Gi 0/2 rx interface Port-based
20 Gi 0/15 Gi 0/3 rx interface Port-based
30 Gi 0/16 Gi 0/37 rx interface Port-based
100 Gi 0/25 Gi 0/38 tx interface Port-based
110 Gi 0/26 Gi 0/39 tx interface Port-based
300 Gi 0/17 Gi 0/1 tx interface Port-based
FTOS(conf-mon-sess-300)#
Port-Pipe 0
Port-Pipe 1
Port-Pipe 0
MD
M
onitor Session 0 MG
MD
M
onitor Session 1
M
onitor Session 2
Port Monitoring 0
03
Line Card 0 Line Card 1
Port-Pipe 1
MD
MD MG
MD
MG
MD
MG