Allowing multiple mac addresses on the same network?

[ajdtech.service@gmail.com]

Hi, please bear with me as I don't have a lot of experience with Cisco switches.

I have an issue where we have several Card Printers on the same network with the same mac address, they are all set as Static IP. Everything was working fine when we had D-Link switches, they all worked fine.

Since the Switches were replaced with Cisco Switches, we've had database servers go down, we will reboot them and they will start working again for a time, then go down again. All the card printers lock up periodically and also need to be rebooted. I sent many pings to each printers and when they are being used, there are multiple timeouts and delays.

Is there a way to tell the Cisco switch to allow this? or do we need to replace these card printers?

[Mark Malone]

Hi
how have they got the same mac addresses, macs are supposed to be globally unique or else you'd have to separate them with some L3 boundary , you cant have same macs in same l2 domain or it will confuse the switches , macs should be unique on a lan, the dlink must have had some method of protection to prevent this automatically breaking the network , when there trying to communicate it resolves to arp and it will see diff ips with sae macs in different locations so it will be constantly intermittent as when the frames are received the ,ac table will keep updating between say 2 ports that have the same mac

[ajdtech.service@gmail.com]

I have no idea, the printed mac address on the barcode is different from the
internal mac address.

I was just wondering if you can tell the Cisco switch about this so it
doesn't keep breaking the network.

[Mark Malone]

You would have to spoof the mac or break the boundary between them if their the same , the mac you need to check is what's been seen at the interface level like below, the Cisco switch is operating as switches usually would default when there is a duplication in it , intermittent responses as at layer 2 its not really sure where the device is physically located as when it resolves back it keeps changing as the mac table is updated each time from the hosts with same mac

xxxxx#sh mac address-table interface g1/0/14
Mac Address Table
-------------------------------------------

Vlan Mac Address Type Ports
---- ----------- -------- -----
1 14fe.b5df.ca1b DYNAMIC Gi1/0/14
Total Mac Addresses for this criterion: 1

If the macs really are the same your logs should also be showing you some for of duplication logs ?
the only way to prevent it is either spoof the mac or create boundarys at l3 between the macs

I have no idea, the printed mac address on the barcode is different from the
internal mac address.
This would suggest there different macs on the physical interface , please use the command above on one of the switches where the printers are connected to confirm there either diff or the same its quite important as it could be the cause

do you have any logs off the cisco switches when it happens ?

[paul driver]

Hello

Curious - what makes you think these card printers had/have the same MAC address?

Res

Paul

[ajdtech.service@gmail.com]

Because there is a spot on the front of the card printers to display the current SN, mac address, current IP, etc. 
There is also a barcode on it that shows the hardware mac address, they are both different.
Each card printer shows the same mac address on the front status. The same mac address for all those printers also shows in the router.
It's very odd.

[paul driver]

Hello
Do you think it may mean all those printers point to the same rtr interface and it’s MAC address

As mark rightly stated hardware MAC address are unique and as such shouldn’t conflict but it for some reason their ip addresses were to be configured the same then it would cause connection issues

How many card printers do you have?
Would it be possible to disconnect them and check their assigned static up addressing

Also do you have dhcp servers as you may need to cross check with these to make sure the card printers static ip addresses are not being allocated to other hosts whilst they are off line .

Res
Paul

[Deepak Kumar]

After read complete conversation, I surprised with your devices mac address. But I don't believe because I have never seen it before. 

Now, I have a solution for you - decrease the mac-address-table ageing-time but keep in mind that it will also make some issues as RTO and High CPU uses. 

Regards,

Deepak Kumar

[paul driver]

Hello

---

@Deepak Kumar wrote:

After read complete conversation, I surprised with your devices mac address. But I don't believe because I have never seen it before. 

Now, I have a solution for you - decrease the mac-address-table ageing-time but keep in mind that it will also make some issues as RTO and High CPU uses. 

Regards,

Deepak Kumar

---

Hello Deepak,

This wouldn't assist in duplicate ip or mac addressing it would only decrease the aging of the switch cam table and probably cause unnecessaryflooding

res
Paul

[ajdtech.service@gmail.com · Accepted solution]

Just so everyone knows...THE PROBLEM HAS BEEN RESOLVED.
The issue stemmed from glitchy firmware in the card printers.The customer's card printers were Polaroid brand, but before they were Polaroid, they were Datamax. When the firmware was updated to Polaroid before they were sold, they had a glitch where if the user selected "reset this page to default" it would completely reset the whole printer including all logins and pages and reset the mac address to the old Datamax defaults. Via Polaroid support, I found a special way to log into each printer through a username called "WebService" and was able to change the mac address back to what it was on its physical barcode. Once that was done and saved, all mac addresses were different and things started to work normally again.