I'm trying to setup my new CRS125-24G-1S-RM up as a SOHO router+switch.

I currently have a spare laptop connected to port 2 to do Webfig since I run linux and I don't really need much in the way of advanced configuration.

When trying to setup things using the Quick Set option I found that if I leave the default MAC address that I get a really wierd IP configuration from my Comcast cable modem, in fact the only addresses that are the same as when connected to my failing Netgear FVS318G are the DNS servers. I can only assume that this is due to the MAC difference so I am trying to "clone" the external MAC from my Netgear router to my CRS125 but as soon as I apply the new MAC I lose all connectivity to the CRS125.

While I'm fairly technical but not in the IT business, I seem to be missing something here.

Thanks,
Richard

Try with this command in terminal
/interface ethernet set ether1 mac-address=xxx
Edit the ethernet interface ether1 to the interface you need to change the MAC-address
Try to use winbox this is match better.
See on my website http://www.wirelessinfo.be/index.php/mi ... es/winboxe

1. Install winbox on your computer and connect to the switch
2. Extract a port from the switch (e.g. ether24 by setting master = none in the interface menu)
3. Add an address to that port, in another subnet (IP->address, say 192.168.10.1/24)
4. Check/enable neigbor discovery on it (IP->neighbors->discovery interfaces)
5. Check that under tools you have MAC access via winbox on all ports (tools->mac server->winbox interfaces)
6. Connect your computer to the independent port (ether24 in this example)
7. Reconnect using Winbox via MAC address (in the neighbor tab click on the mac address)
8. Change the MAC of any port you want EXCEPT ether24

i believe the correct way to do this would be to remove the last port from the switch group, connect to the switch via THAT port and it's MAC address. Then you can change the master port (ether1 normally) MAC address without being disconnected.

The disconnection is normal and expected. When you change the MAC, the port needs to be taken offline, then the MAC is changed, and the port comes back up. Next the IP will not match the MAC, so you will lose IP connection. The Master Port's MAC covers all of the switch ports that are slave to it. So, when you take a port out of the switch group (setting master=none), it can have it's own IP/etc.

Hope this helps.