Reference Guide
Port Monitoring | 767
In the example below, 0/25 and 0/26 belong to Port-pipe 1. This port-pipe again has the same restriction of
only four destination ports, new or used.
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)#
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 41-1 illustrates conceptually the
possible port monitoring configurations on the C-Series and S-Series.
Figure 41-2. 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 and S-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.
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