Switching inconsistency on WS-C2960S-48TD-L

[Konstantin Kabassanov]

Hello,

A really strange thing happened today on a WS-C2960S-48TD-L running c2960s-universalk9-mz.122-58.SE2.bin

We changed the uplink port from "GigabitEthernet1/0/49", DESCR: "1000BaseSX SFP" to "TenGigabitEthernet1/0/2", DESCR: "SFP-10GBase-

SR" (in 2 differents SFP+ slots).

The MAC address of one of our servers, accessible through the uplink, appeared on the new interface :

show mac address-table address 00:15:17:cc:2f:af

          Mac Address Table

-------------------------------------------

Vlan    Mac Address       Type        Ports

----    -----------       --------    -----

 315    0015.17cc.2faf    DYNAMIC     Te1/0/2

Total Mac Addresses for this criterion: 1

But outgoing packets are still forwarded incorrectly on GigabitEthernet1/0/49.

We have excluded this vlan number on the old uplink interface for some seconds and traffic is correctly forwarded now, but this behavior remains strange for me.

Any idea?

Thanks.

[Philip D'Ath]

I would say something was still being cached and had not updated itself.  The approach you took to resolve it was a good one.  I suspect it would also have updated itself within 10 minutes.

How do you know traffic was still going on the GigabitEthernet1/0/49? for the host concerned?

[Konstantin Kabassanov]

In fact, it had not updated for more than 4 hours.

And it was not really easy to detect the origin, because there was some correct traffic in this vlan for at least one entry on the new link: the gateway. So pings to the gateway or Internet were succesful.

I used an RSPAN monitor session that I first connected to the inbound  switch port. I got my test packets. After that, I attached the source of the monitor session to the uplink port and didn't see them anymore. And when I repeated the same thing on the old uplink port, I saw them again.