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vk2mpj
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2 Routers with same MAC addresses?

Wed May 24, 2023 1:14 pm

Hi all,

I have an strange one that has me scratching my head.
I have the following MikroTik items in my network
RB960PGS (hEX PoE) - The main router and CAPsMAN
RB962UiGS-5HacT2HnT (hAP ac) - In CAP mode
2x RBD52G-5HacD2HnD (hAP ac2)- In CAP mode

I have been having issues when trying to connect to either the hEX or one of the hAP ac2 via MAC in Winbox, where it seems to get confused and not connect me to the right one.
I have just been dealing with it and connecting via IP, but a few other issues have had me looking deeper into this and I have found that the hEX PoE and one of the hAP ac2 appear to have the same MAC addresses on their interfaces. Albeit they aren't a direct correlation, but you can see below that the same MAC addresses are still present on the ethernet interfaces none the less.
I have never seen this before, and I have no idea how it has happened.

Is there anyway I can fix this? I have had a look around WinBox, tried the "Reset MAC Address" under each interface, but that made no difference.

Any help would be greatly appreciated.
# may/24/2023 19:45:02 by RouterOS 7.9.1
# software id = QGB7-IR02
#
# model = RB960PGS

Flags: D - DYNAMIC; R - RUNNING; S - SLAVE
Columns: NAME, TYPE, ACTUAL-MTU, L2MTU, MAX-L2MTU, MAC-ADDRESS
 #     NAME         TYPE       ACTUAL-MTU  L2MTU  MAX-L2MTU  MAC-ADDRESS      
 0  R  ether1       ether            1500   1598       4074  DC:2C:6E:1D:9E:5C
 1  RS ether2       ether            1500   1598       4074  DC:2C:6E:1D:9E:5B
 2  RS ether3       ether            1500   1598       4074  DC:2C:6E:1D:9E:5A
 3  RS ether4       ether            1500   1598       4074  DC:2C:6E:1D:9E:59
 4   S ether5       ether            1500   1598       4074  DC:2C:6E:1D:9E:58
 5     sfp1         ether            1500   1600       4076  B8:69:F4:B3:A3:25
# may/24/2023 19:16:18 by RouterOS 7.9.1
# software id = SDG2-XIMK
#
# model = RBD52G-5HacD2HnD

Flags: D - DYNAMIC; R - RUNNING; S - SLAVE
Columns: NAME, TYPE, ACTUAL-MTU, L2MTU, MAX-L2MTU, MAC-ADDRESS
#     NAME         TYPE    ACTUAL-MTU  L2MTU  MAX-L2MTU  MAC-ADDRESS      
0  RS ether1       ether         1500   1598       9214  DC:2C:6E:1D:9E:58
1   S ether2       ether         1500   1598       9214  DC:2C:6E:1D:9E:59
2  RS ether3       ether         1500   1598       9214  DC:2C:6E:1D:9E:5A
3   S ether4       ether         1500   1598       9214  DC:2C:6E:1D:9E:5B
4   S ether5       ether         1500   1598       9214  DC:2C:6E:1D:9E:5C
 
vk2mpj
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Re: 2 Routers with same MAC addresses?

Mon May 29, 2023 2:25 am

So in the intervening time that it took for this post to be approved ( not sure why it took so long) I have found the root cause.

I had previously been using the hAP ac2 as the main router, when I decided to switch to the HEX PoE I took a back up of the hAP and then loaded that to the HEX. This in turn has changed the MAC addresses of the HEX to be those of the hAP.

I identified this by exporting the config and read through it until I identified where it changed the MAC addresses of the interfaces.
Interesting to note that the “REST MAC” button in WinBox didn’t work, but using the CLI did. Now the MAC addresses are back to default and the issues have been resolved.
 
tdw
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Re: 2 Routers with same MAC addresses?

Mon May 29, 2023 2:10 pm

From the documentation "RouterOS backup feature allows you to save the current device's configuration, which then can be re-applied on the same or a different identical model. This is very useful since it allows you to effortlessly restore the device's configurations or to re-apply the same configuration on a backup device. The system's backup file also contains the device's MAC addresses, which are also restored when the backup file is loaded."

I've highlighted a key point - restoring a backup on a different hardware model may result in all sorts of unspecified behaviour, this can be interfaces appearing in the wrong order or not at all, and/or some functions just not working. The correct method is to use an /export and adapt it for the new model in this situation.
 
vk2mpj
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Re: 2 Routers with same MAC addresses?

Tue May 30, 2023 6:42 am

From the documentation "RouterOS backup feature allows you to save the current device's configuration, which then can be re-applied on the same or a different identical model. This is very useful since it allows you to effortlessly restore the device's configurations or to re-apply the same configuration on a backup device. The system's backup file also contains the device's MAC addresses, which are also restored when the backup file is loaded."

I've highlighted a key point - restoring a backup on a different hardware model may result in all sorts of unspecified behaviour, this can be interfaces appearing in the wrong order or not at all, and/or some functions just not working. The correct method is to use an /export and adapt it for the new model in this situation.
Thanks mate.
Yes this is something I have learned from this experience. I now not only have a back up file, but I have also exported the working config and saved that for future use if requried.
 
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mkx
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Re: 2 Routers with same MAC addresses?

Tue May 30, 2023 8:36 am

@vk2mpj: don't take the post personally. The same problem happens often enough that people replying to posts like yours will often phrase the reply in the way some users find a little too harsh (that's not the way @tdw replied IMO). But let's say it's for other users' sake - if enough replies contain "don't restore backup file on different type of device", then ChatGPT might pick it up :wink:

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