rattkin.info

When you move Sophos UTM to a new box, or change all network interfaces, webadmin becomes unreachable. It is possible to set new ip address to an interface (ifconfig 192.168.1.1 netmask 255.255.255.0 eth0 && ifconfig up eth0) but then it is not possible to change any network interfaces.

Instead, use the command line to add new hardware to existing interface object:

cc
RAW
lock_override
OBJS
interface
ethernet

<TAB><TAB>       (this will show a list of the ethernet interface objects which are the Internal and External sophos interfaces. Both objects will likely begin with REF_ so pressing <TAB><TAB> will show the full object and you will need to type the next unique letter and then press <TAB> again to autocomplete. It is case sensitive.) REF_DefaultInternal[Internal,interface,ethernet]
{the object will be shown along with it's parameters and values}

itfhw=<TAB><TAB>
           {the new ETH1 and ETH2 "hardware" NIC card objects will be listed beginning with "REF_ItfEthEth"  (your objects will likely be named differently)}

itfhw=REF_ItfEthEth1<TAB>
            {shows the full object for ETH1 and all I have to do is press <enter> to select it}

status=1
            {the NIC was "down" and changing status=1 brings it UP to working order}

w
             {w - writes the change and the object repaints with the nic card added to the Hardware param}

quit

The NIC should now be up and functioning and you can check by doing an ifconfig on the command line to see it has been added.

Source:

https://community.sophos.com/products/unified-threat-management/f/hardware-installation-up2date-licensing/87012/webadmin-access-through-eth1-which-needs-to-be-added-via-command-line