Inappropriate traffic on switch port

[constantin.blanariu]

Hi,

We have an issue on a 4507. On a port there is traffic that should be destined to another port. The traffic is destined to another

IP, one that was not on that port. The weird thing is that the MAC address coresponding to that IP is showing on the right port,

as dynamically learned.

When we statically put that MAC address to the right port, the traffic stops showing up on the wrong port. What could happen here ?

Thank you very much,

Constantin

[lgijssel]

What was the mac address?

[constantin.blanariu]

It is an unicast MAC address.

[lgijssel · Accepted solution]

You are well informed about my initial thoughts.

Well, I am prepared to accept that you are capable to notice the difference so that should not be the reason.

There are situations in which unicast traffic can be flooded as well.

With the minimal information that you are aparently willing to provide, it will be mere guesswork what the cause might be.

Please check the link below and determine if one of the scenario's matches your situation.

http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note09186a00801d0808.shtml

regards,

Leo

[constantin.blanariu]

Hey, Leo!

Thank you for your answer. I checked the resources you provided  and, although the situations are interesting,

that is not our case. Our problem can be reduced to this: we have only one switch, with three hosts attached,

all in the same VLAN. The mac addresses of the three hosts appear where they should be.

When two of them ping each other, the traffic shows up on the interface connecting to the third host. Even if we

put the MAC addresses statically on their appropriate ports, the traffic shows up on the third. We have put the

4 hours MAC aging time.

This is very strange and any idea is welcomed.

Thank you,

Constantin

[lgijssel]

Hi Constantin,

This is not normal behavior.

Did you check the third interface is not set up as a monitor port?  Or is that too obvious?

Or perhaps the config involves private vlans?

In that case, I would modify it to a normal vlan and see if the problems goes away.

regards,

Leo

[constantin.blanariu]

Hi, Leo!

The situation I described earlier with the switch and the three connected hosts was a confusion from our side, traffic from the wrong port

was routed in the RSPAN VLAN to be monitored. I am trully sorry for the confusion I created. The switch behaves normally with the

4 hour MAC aging time.

We will keep monitoring the switch and post here if something goes wrong.

Thank you for your patience and answers,

Constantin