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Dell EMC Configuration Guide for the S3100 Series 9.14.2.4

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Port Monitoring

Port monitoring is supported on both physical and logical interfaces, such as VLAN and port-channel interfaces. The source port (MD) with monitored traffic and the destination ports (MG) to which an analyzer can be attached must be on the same switch. You can configure up to 128 source ports in a monitoring session. Only one destination port is supported in a monitoring session. The platform supports multiple source-destination statements in a single monitor session.

The maximum number of source ports that can be supported in a session is 128.

The maximum number of destination ports that can be supported depends on the port mirroring directions as follows:
  • 4 per port pipe, if the four destination ports mirror in one direction, either rx or tx.
  • 2 per port pipe, if the two destination ports mirror in bidirection.
  • 3 per port pipe, if one of the destination port mirrors bidirection and the other two ports mirror in one direction (either rx or tx).

Example of Changing the Destination Port in a Monitoring Session

In the following examples, ports 1/13, 1/14, 1/15, and 1/16 all belong to the same port-pipe. They are pointing to four different destinations (1/1, 1/2, 1/3, and 1/37). Now it is not possible for another source port from the same port-pipe (for example, 1/17) to point to another new destination (for example, 1/4). If you attempt to configure another destination (to create 5 MG port), this message displays: % Error will be thrown in case of RPM and ERPM features.

DellEMC(conf-mon-sess-5)#do show moni session
  SessID  Source         Destination         Dir  Mode  Source IP      Dest IP    DSCP  TTL   Drop  Rate    Gre-Protocol FcMonitor
  ------  ------         -----------         ---  ----  ---------      --------   ----  ---   ----  ----    -----------  ---------
     1   Gi 1/1            Gi 2/1            both Port     N/A            N/A      0     0    No    N/A        N/A        yes
     2   Gi 1/1            Gi 2/2            both Port     N/A            N/A      0     0    No    N/A        N/A        yes
     3   Gi 1/1            Gi 2/3            both Port     N/A            N/A      0     0    No    N/A        N/A        yes
     4   Gi 1/1            Gi 2/4            both Port     N/A            N/A      0     0    No    N/A        N/A        yes
     5   Gi 1/1            Gi 2/5            both Port     N/A            N/A      0     0    No    N/A        N/A        yes
DellEMC(conf-mon-sess-5)#
DellEMC(conf)#mon ses 300
DellEMC(conf-mon-sess-300)#source gig 1/17 destination gig 1/4 direction tx
% Error: Exceeding max MG ports for this MD port pipe.
DellEMC(conf-mon-sess-300)#
DellEMC(conf-mon-sess-300)#source gig 1/17 destination gig 1/1 direction tx
DellEMC(conf-mon-sess-300)#do show mon session
SessID  Source         Destination      Dir  Mode       Source IP    Dest IP      DSCP  TTL   Drop  Rate    Gre-Protocol FcMonitor
------  ------         -----------      ---  ----       ---------    --------     ----  ---   ----  ----    -----------  ---------
  0     Gi 1/13           Gi 2/1        rx   interface   0.0.0.0     0.0.0.0       0     0    No    N/A        N/A        yes
  10    Gi 1/14           Gi 2/2        rx   interface   0.0.0.0     0.0.0.0       0     0    No    N/A        N/A        yes
  20    Gi 1/15           Gi 2/3        rx   interface   0.0.0.0     0.0.0.0       0     0    No    N/A        N/A        yes
  30    Gi 1/16           Gi 2/7        rx   interface   0.0.0.0     0.0.0.0       0     0    No    N/A        N/A        yes
  300   Gi 1/17           Gi 1/1        rx   interface   0.0.0.0     0.0.0.0       0     0    No    N/A        N/A        yes
DellEMC#

Example of Configuring Another Monitoring Session with a Previously Used Destination Port

DellEMC(conf)#monitor session 300
DellEMC(conf-mon-sess-300)#$ destination gigabitethernet 1/4 direction tx
DellEMC(conf-mon-sess-300)#
DellEMC(conf-mon-sess-300)#do show monitor session
  SessID  Source         Destination         Dir  Mode  Source IP      Dest IP         DSCP  TTL   Drop  Rate     Gre-Protocol FcMonitor
  ------  ------         -----------         ---  ----  ---------      --------        ----  ---   ----  ----     -----------  ------
     0   Te 1/50           Te 1/51           rx   Port     N/A            N/A          N/A   N/A   No     N/A         N/A      yes
     1   Gi 1/45           Gi 1/46           tx   Port     N/A            N/A          N/A   N/A   No     N/A         N/A      yes
     2   NONE              NONE              N/A  N/A      N/A            N/A          N/A   N/A   No     N/A         N/A      No
   300   Gi 1/17           Gi 1/4            tx   Port     N/A            N/A          N/A   N/A   No     N/A         N/A      No
DellEMC(conf-mon-sess-300)#

Example of Viewing a Monitoring Session

In the example below, 0/25 and 0/26 belong to Port-pipe 1. This port-pipe has the same restriction of only four destination ports, new or used.

DellEMC(conf-mon-sess-300)#do show mon session
SessID  Source      Destination    Dir  Mode      Source IP      Dest IP   DSCP  TTL   Drop  Rate    Gre-Protocol FcMonitor
------  ------      -----------    ---  ----      ---------      --------  ----  ---   ----  ----    -----------  ---------
 0      Gi 1/13       Gi 2/1       rx   interface     N/A          N/A      0     0    No    N/A        N/A        yes
 10     Gi 1/14       Gi 2/2       rx   interface     N/A          N/A      0     0    No    N/A        N/A        yes
 20     Gi 1/15       Gi 2/3       rx   interface     N/A          N/A      0     0    No    N/A        N/A        yes
 30     Gi 1/16       Gi 2/4       rx   interface     N/A          N/A      0     0    No    N/A        N/A        yes
 100    Gi 1/25       Gi 2/5       tx   interface     N/A          N/A      0     0    No    N/A        N/A        yes
 110    Gi 1/26       Gi 2/5       tx   interface     N/A          N/A      0     0    No    N/A        N/A        yes
 300    Gi 1/17       Gi 2/5       tx   interface     N/A          N/A      0     0    No    N/A        N/A        yes   
DellEMC(conf-mon-sess-5)#

Given these parameters, the following illustration shows the possible port monitoring configurations.

Figure 1. Port Monitoring Configurations
Illustration of port monitoring configurations.

Dell EMC Networking OS Behavior: All monitored frames are tagged if the configured monitoring direction is egress (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 6/1 destination Gig 6/2 direction tx, if the MD port Gig 6/1 is an untagged member of any VLAN, all monitored frames that the MG port Gig 6/2 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.

Dell EMC Networking OS Behavior: The platform continues to mirror outgoing traffic even after an MD participating in spanning tree protocol (STP) transitions from the forwarding to blocking.

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