MAC address table.

Answered Question
Jun 20th, 2007
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A desktop is connected to a stand alone switch. while doing 'sh mac-address-table' the desktop mac-address is showing two time in the table. Is it normal or abnormal? If it is abnormal than how to solve it? Please advice.Thx.

Correct Answer by guruprasadr about 9 years 11 months ago

HI,


Use the below command:


clear mac-address-table [dynamic | restricted static | permanent] [address mac-address] [interface type module/port]


You can clear the Mac-Address in the Table based on your requirement. This will not affect other Ports / Interface whichever learnt something Important.


"clear mac-address-table [interface type module/port]" - Hope This command will help you check the Issue....



PLS Rate if HELPS


Best Regards,


Guru Prasad R

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royalblues Wed, 06/20/2007 - 21:36
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Arun,


Do you mean to say that you see the mac-address learnt on 2 different ports?


Narayan

arun_patro2001 Wed, 06/20/2007 - 22:47
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Hi Narayan ,


Yes, The mac-address learnt & shows connected through two different port.


Arun

smothuku Wed, 06/20/2007 - 21:38
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Hi ,


Try tyo clear arp entries using clear arp-cache ot clear ip arp and check the issue.


Thanks,

Satish.

Correct Answer
guruprasadr Wed, 06/20/2007 - 22:22
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HI,


Use the below command:


clear mac-address-table [dynamic | restricted static | permanent] [address mac-address] [interface type module/port]


You can clear the Mac-Address in the Table based on your requirement. This will not affect other Ports / Interface whichever learnt something Important.


"clear mac-address-table [interface type module/port]" - Hope This command will help you check the Issue....



PLS Rate if HELPS


Best Regards,


Guru Prasad R

royalblues Wed, 06/20/2007 - 22:52
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yes try clearing the mac address table.


it is very unlikely though cos when a switch learns the same mac-address on other port it updates its mac address table..


Satish, clearing the arp entries will not help. if its a L2 switch then it will an arp entry for only its gateway


HTH

Narayan

arun_patro2001 Wed, 06/20/2007 - 23:43
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Hi , Thanks to all for your information. I will try this after office hour & rate according if it resolves. Thanks again.


Arun

mohammedmahmoud Thu, 06/21/2007 - 04:56
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Hi,


Totally agree with Narayan, the mac table is to be cleared and not the ARP table, arp table will have only any IP/MAC address that was used to ping or telnet to the Layer 2 switch plus the default-gateway of the switch (only IP/MAC mapping due to ARP requests with the appropriate interface - Interface VLAN1), and won't have all the MAC addresses of the directly connected hosts and there respective interfaces (this is the responsibility of the mac table).



HTH,

Mohammed Mahmoud.

vinayrajkp Thu, 06/21/2007 - 04:39
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Did u try to connect the desktop to one port and then disconnect and connect to another port and checked the mac-address immediately after that?


Did you check the entry long after that? Did it disappear - i mean one of the entries?


Which two ports are showing the mac-addresses? what are connected to each of these?


Is there any static arp command configured?


finally is it possible to reboot the switch and check?


Guess if you try to find answers to these questions then you may find the reason to the problem.

arun_patro2001 Thu, 06/21/2007 - 23:11
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Hi ,


I have cleared the MAC address table of the switch & found the problem got resolved. But still trying to find the root couse as this happened for the 1st time. Can anyone provide some information.


Thanks

Arun

guruprasadr Thu, 06/21/2007 - 23:28
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HI Arun,


It's always quiet interesting to find the Root Cause for any Problem.


If you have any "Logs" related to this Issue then we can identify the Root Cause.


Else, you need to verify the Bug Reports of the IOS Version/Release.


Pls Rate all Helpful Replies.


Best Regards,


Guru Prasad R

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