Strange MAC counters

[jgercken]

I'm working on a script to compile and sort through our 6500s' mac counters and randomly chose this port for a syntax example. The port is disconnected (for how long ???) but the stats seem very strange. Though I'd share and request comments...

-Jeff

s64-e-1> (enable) sh mac 9/11

Port Rcv-Unicast Rcv-Multicast Rcv-Broadcast
-------- -------------------- -------------------- --------------------
9/11 0 0 1

Port Xmit-Unicast Xmit-Multicast Xmit-Broadcast
-------- -------------------- -------------------- --------------------
9/11 192592 16500346 74964025

Port Rcv-Octet Xmit-Octet
-------- -------------------- --------------------
9/11 66 36561960671

MAC Dely-Exced MTU-Exced In-Discard Out-Discard
-------- ---------- ---------- ---------- -----------
9/11 0 0 0 0

Last-Time-Cleared
--------------------------
Sat May 18 2002, 17:32:42
----------------------------------------
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[dnels]

OK, I can see the 1 rcv-broadcast for 66 bytes being a BPDU meaning this was connected to another switch. The switchport on the other side of this port is probably blocking. The broadcasts will be forwarded on all ports of the vlan and dropped on the other switch. The multicast is probably 224.0.0.x such as hsrp. The puzzler is where are the unicasts coming from?

 

[dnels]

DUH, Unicast frames to a destination whose entries are not in the cam table are flooded to all ports in the vlan.

Dave

 

[jgercken]

Makes sense. Interesting that the counters increment even when the interface is down. Guess they're pulled from the port's ASIC which continues to operate and just keeps overflowing the xmit buffer.

Adds a twist to my accounting script. Wonder what the switch would return from a RMON query on this port.
-Jeff ----------------------------------------
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