2

I have a Cisco router with NM-16ESW switch module (all virtual, on GNS3). Switch is connected to a router and two hosts and there is heavy simulated traffic passing through the switch. However, interface counters show zero input and output. What could be the cause of this issue?

ESW3#show int counters

Port            InOctets   InUcastPkts   InMcastPkts   InBcastPkts
Fa1/0                  0             0             0             0
Fa1/1                  0             0             0             0
Fa1/2                  0             0             0             0
Fa1/3                  0             0             0             0
Fa1/4                  0             0             0             0
Fa1/5                  0             0             0             0
Fa1/6                  0             0             0             0
Fa1/7                  0             0             0             0
Fa1/8                  0             0             0             0
Fa1/9                  0             0             0             0
Fa1/10                 0             0             0             0
Fa1/11                 0             0             0             0
Fa1/12                 0             0             0             0
Fa1/13                 0             0             0             0
Fa1/14                 0             0             0             0
Fa1/15                 0             0             0             0

Port           OutOctets  OutUcastPkts  OutMcastPkts  OutBcastPkts
Fa1/0                  0             0             0             0
Fa1/1                  0             0             0             0
Fa1/2                  0             0             0             0
Fa1/3                  0             0             0             0
Fa1/4                  0             0             0             0
Fa1/5                  0             0             0             0
Fa1/6                  0             0             0             0
Fa1/7                  0             0             0             0
Fa1/8                  0             0             0             0
Fa1/9                  0             0             0             0
Fa1/10                 0             0             0             0
Fa1/11                 0             0             0             0
Fa1/12                 0             0             0             0
Fa1/13                 0             0             0             0
Fa1/14                 0             0             0             0
Fa1/15                 0             0             0             0
4

The cause of this is most likely GNS3. Virtual/emulated platforms simply won't have all the same characteristics and behaviors as real hardware.

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4

While GNS3 can somewhat emulate a switch functionality by utilizing the NM-16ESW, it cannot do so fully because of the same reasons it can't emulate a switch. Many of the features are simply embedded into the hardware.

Since switch forwarding is often done only in hardware, the processes to provide statistics about that traffic are also in hardware. Without those processes to feed the data back to the router, you end up with no statistics for those ports.

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