mac address lookup

[jmgutierrezjr]

Hello,

I'm hoping someone can help me out.  In the past I was able to use this tool to lookup the mac address of any machine connected to this switch, but this is no longer the case.  When I run show mac-address-table address xxxx.xxxx.xxxx, I receive a message with "no entries present" and as I mentioned, in the past I would receive the switch port that the device was connected to.

[Leo Laohoo]

The MAC address you are looking for is no longer stored in the CAMs table.

If you happen to know the IP address ping that and run the command again.

Another trick (not fool-proof) is to ping the broadcast IP address and try the command again.

[jmgutierrezjr]

I thought this also and still did not work.  I run this command on my other switches with no issue, it appears to be this and one more switch not finding the MAC addresses. 

Also, I was able to locate the port/mac by just running "show mac-address-table" and sifting through over 300 macs.  Just wanted to go faster by using the OP command to no avail.

[acampbell]

Hi,

How about trying

show mac-address-table | inc aaaa.bbbb.cccc

Regards

Alex

[jmgutierrezjr]

you are my hero!! Thanks Alex. 

So any chance you can help me understand why this works on my other switches and not this particular one unless I do the | inc?

What is | inc do?

[Richard Burts]

Jose

the | inc is a feature that uses regular expressions to select certain records that match a particular string. The inc is actually an abbreviation for include.  So the command is actually | include aaaa.bbbb.cccc and it will result in showing the mac address table only values that match the string aaaa.bbbb.cccc

There are quite a few show commands for which the | include is very handy. I frequently like to do show log | include to find certain events in the router syslog buffer file. Or show run | include to find certain type of lines in the configuration.

As for why the show mac-address-table command works on some of your switches but not on this one I would guess that either this one switch is a different model switch from the others or that this one switch is running a version of code than the others. In my experience on lots of older switches the command was show mac-address-table and on some of the newer switches the command has become show mac address-table (notice no hyphen between mac and address). Can you tell us the model and version of code where your command does not work and model and version of code where your command does work?

HTH

Rick

[acampbell]

Jose,

First of all lets thank Rick for his expanation (+5 Rick)

And as Rick has stated your command

show mac-address-table address aaaa.bbbb.cccc

or

show mac-address-table | include aaaa.bbbb.cccc

Should both work on 3550.2950 etc

May be you have hit a bug, can you tell us what the model and IOS versions are.

Regards

Alex

Please rate useful posts.

[jmgutierrezjr]

Hardware: C6509

Non-working show mac-address-table address is running on

Cisco IOS Software, s72033_rp Software (s72033_rp-IPSERVICESK9_WAN-M), Version 12.2(33)SXJ1, RELEASE SOFTWARE (fc2)

Working device

Cisco Internetwork Operating System Software

IOS (tm) s32p3_rp Software (s32p3_rp-IPBASEK9-M), Version 12.2(18)ZYA3b, RELEASE SOFTWARE (fc2)

[acampbell]

Jose,

On the Sup720

Can you try

show mac address-table add aaaa.bbbb.cccc

Notice NO - (hyphen btween mac & address)

Regards

Alex

[jmgutierrezjr]

no luck

[Richard Burts]

Jose

I checked on a 6504 with Sup 720 which is running software slightly different from what you are running. I found that my 6504 works as expected with both forms of the command. It worked with show mac-address-table address and worked with show mac address-table address. At first I was quite surprised. And then I noticed somethat that may explain what is going on. I looked more carefully at the software that you are running and I see this:

s72033_rp Software (s72033_rp-IPSERVICESK9_WAN-M),

So you are running the WAN flavor of the image. I do not know it as authoritative but I believe that the WAN version of the software does not support the command since it is a LAN function.

HTH

Rick

[fb_webuser]

Check your DHCP tables for the mac address then you can find the IP address to ping. Once the ping goes through, you should be able to trace the mac if the client is up.

---

Posted by WebUser Adam Sibille