You can indeed make this change, but agree it does not always look like the most obvious thing.
First, it depends if you intend to use DHCP after the change or not. If you are, do the following first.
1: Login to the route
2: Select Home Network from the left
3: Select Interfaces on the section that opens out on the left.
4: Click the LocalNetwork at the top of the tree in the centre of the screen
5: In the top right, select Configure
6: Untick "Use DHCP" and click Apply
7: Perform step 5 again
8: In the DHCP Pools section, select the edit link (will not be present unless you have performed steps 6 & 7).
9: Ensure you set the "Start Address", "End Address", "Server", "Gateway" values ("Server" & "Gateway" should be the values you want the router to be) and Apply at the bottom
10: Again perform step 5
11: Tick the "Use DHCP" checkbox and Apply
To change the routers IP, follow steps 1 through 5 above, then
6: In the IP Addresses section, select Edit next to the existing IP (do not edit or remove the 10.0.0.138 item)
7: Set the New IP of the router, there should be no need to edit the Mask
8: Apply this
You will note it looks like the router has failed, this is normal, simply because the IP has changed and your PC is not connecting to the correct IP.
Either force a new IP by resetting your network adaptor if using DHCP, or manually change your computers IP. Your router will now be on the new IP.
One thing to note. I see this every now and again. Once the IP has been changed, your router may persistently ask you to login, this can be resolved by leaving it for 5 minutes and rebooting it. It will remain on the new IP and should stop persistently asking you to login again.
