Trace mac address that belong to vlan mac address

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Sep 29th, 2009
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Say i have an duplicate ip address which i need to trace the switch and port.

I used "show ip arp" to trace from Distribution Switch A and came to know that the mac address is xxxx.xxxx.xxxx

However i found that the mac-address belong to vlanY. It also display a lot of different ports mapped to this mac-address as static router.

How should i find where the switch and port belong to this duplicate address?

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xcz504d1114 Tue, 09/29/2009 - 07:53
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Your router that has the IP address, will generate a log statement saying device xxxx.xxxx.xxxx has the same IP address.

Make sure logging is enable:

conf t

logging buffer

and you can view the output of the buffer by using "show log".

In some cases you may have a lot of log messages that fill up the buffer quickly, you can vary the size of the buffer, but that does consume resources, so you might want to setup a syslog server if you don't already have one. Kiwi is a good choice for a syslog server. Then you can keep a larger record of your logs without consuming local router resources.



kian_hong2000 Tue, 09/29/2009 - 07:54
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I notice that vlanY appear at both Distribution Switch A and B.

Where in DSB

Duplicate address on VlanX, sourced by AAAA.AAAA.AAAA

Where in DSA

Duplicate address on VlanX, sourced by BBBB.BBBB.BBBB

But i check the two vlan interfaces and both does not have duplicate addresses. This duplicate ip address is part of the subnet where both vlanX support.

However, the HSRP addresses for both interfaces are different but using the same subnet as the duplicate addresses. Where could go wrong?

xcz504d1114 Tue, 09/29/2009 - 11:42
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Post your HSRP configuration for both DSA and DSB.

Also post the output of "show standby brief" for both DSA and DSB.



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