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Community Member

Invalid MAC 0000.0000.0000 Learning on 6509-E

I have two 6509-E switches using portcahnnel.  The second switch continues to learn all zero mac and sends it out to some of my access switches.  The only sniffer captures I can find show up as Fiber Channel Protocol.  Has anyone seen this?  Cisco TAC say's could be a bad NIC or NIC teamng, to find the culprit is process of elimination on switch modules. Any traces I have done only shows source mac of zeros no dest mac.

sh mac-address-table | inc 0000.0000.0000
* 2204  0000.0000.0000   dynamic  Yes        295   Router
* 2210  0000.0000.0000   dynamic  Yes        295   Router
*  ---  0000.0000.0000    static  No           -   Router

4 REPLIES

Re: Invalid MAC 0000.0000.0000 Learning on 6509-E

I have run across this and it turned out to be a bad NIC. If I remember correctly the all zero's mac address means the router does not know what the mac address is. I tracked it down by elimination and removed it, swapped the NIC and all was well again.

Mike

Re: Invalid MAC 0000.0000.0000 Learning on 6509-E

Hi there,

I second Burleyman - I have seen this and it turned out to be a faulty NIC on a batch of machiens, in this case a BIOS update on the effected machiens sorted the problem....

Cheers

Jonathan

Cisco Employee

Re: Invalid MAC 0000.0000.0000 Learning on 6509-E

sh mac-address-table | inc 0000.0000.0000
* 2204  0000.0000.0000   dynamic  Yes        295   Router
* 2210  0000.0000.0000   dynamic  Yes        295   Router
*  ---  0000.0000.0000    static  No           -   Router

This output is quite unusual, not because switch is learning all zero MAC, but the way it is learnt. The output states it's learnt dynamically, however port is still displayed as "Router".

Also, we see it in more than 1 Vlan, so this is certainly coming from a device with multiple L3 interfaces (SVI) configured. Can you share the sniffer traces and specify the interface of which it was taken? Also, let me know the IOS version used + "Sh module" output from both the 6500 switches.

Also check, if any PO interfaces have the mac set as all zero's, via the "sh interface po <>" CLI. Do you have a TAC case opened for this?

Regards,

Deepak

Community Member

Re: Invalid MAC 0000.0000.0000 Learning on 6509-E

Thank You for your reply. All sniffer traces show all zero mac src and dest. And shows as Fiber Channel Protocol. I will send you some of the items you asked for later today.

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