Mac-address Query

[BCSCB]

Morning All,

This may be a stupid question but here goes....

a 3750-12G E Switch mac address 00:13:60D:80:80
Connected to the switch is 6 3560-48 PoE's running standard image.
Switch1 00:17:5A:52:0D:80
Switch2 00:17:5A:52:42:80
Switch3 00:17:5A:81:65:00
Switch4 00:17:5A:52:40:80
Switch5 00:17:5A:3C:76:00
Switch6 00:17:5A:52:43:00

The problem comes when you ping the devices and show the arp table ( SH ARP )

this is what comes back
Protocol Address Age (min) Hardware Addr Type Interface
Internet Switch1 3 0017.5a52.0dc0
Internet Switch2 24 0017.5a52.42c0
Internet Switch3 29 0017.5a81.6540
Internet Switch4 4 0017.5a52.40c0
Internet Switch5 5 0017.5a3c.7640
Internet Switch6 5 0017.5a52.4340

The second to last digit has changed by an increment of 4
0 has changed to 4 8 has changed to c

Does any one know why this happens......

I am getting my nuckles rapped as the asset managemnt team say im not putting the correct Mac address on. (There a strange bunch who check assets from a central switch using Mac address then tally them up )

I dont want to go to them and call them a bunch of Morons without a definitive answer....

 

[robertjo24]

If you do a "Show Version" on the switch, the "Base" MAC address (of the switch)is shown. Each interface will have it's own MAC address. This can be seen by doing a "Show Interface", or see a specific interface "Show Interface F0/X".

 

[jdeisenm]

the show version mac address should match the mac address on a sticker on the back of the switch

 

[BCSCB]

Its only Happens on the newer switches we have a mix of 3560's and 3750's ( Where the problem lies) but it doesnt happen on the 3508's or the 3500's or 3550's

Has the way that the broadcast there mac changed.

So from what your saying Robertjo24 it no longer broadcasts the base mac to its neighbour it broacasts the port mac ?????

Jdeisenm, your right the sticker does match the base mac, but that not the one that you can trace ???

Its as clear as mud.

 

[BCSCB]

I have had a look at the switches,, Robertjo24....

The mac address of the port that it is connected to is 0017.5a3c.7601 thats not the one that is showing on the Distribution switch...

I am at a loss......

Any other thoughts

 

[jdeisenm]

I duplicated the situation.
The mac on a 2950 matches one in the arp table but the mac on a 3560 does NOT match the one in the arp table.

 

[BCSCB]

Im glad Im not going mad !!!

Any Ideas why its like that ?????