What model is this? Router uses 192.168.1.1 not 192.168.1.254. Also read your router instructions on how to login to the router.

The router is a Thomson not sure of model but supplied by plusnet. I have always accessed the router from 192.168.1.254 I have logged in frequently in the past without problems, while no expert, I am sure the problem does not lie with the router and the access address is correct. The problem is that firefox no longer accesses it. I have a Rpi webserver on which I have changed the host name, but nmap -sP shows old name at its (static) address. nmap also detects the router at the normal address,as does ping. Only firefox does not seem to be aware of it. Thanks again for the prompt reply

Regards R.

Then you need to contact the manufacture about the problem since this isn't a FF issue. By default routers uses 192.168.1.1 as the main line to the router and if you changed it or someone else changed it then whom ever did the change needs to fix it. As of now all router regardless for Consumers are 192.168.1.1 to access them-if different then you need to contact the manufacture for support on their router.

WestEnd said

By default routers uses 192.168.1.1 as the main line to the router ...

That is not correct - any LAN address of 192.168.1.### can be used by a router or any other device in the LAN. It's just 192.168.1.1 is more commonly used by routers than any other IP address. edit That depends upon what the router is set to use by the BIOS in the router; some routers have the option to change the IP address internally and some can be "flashed" to modify the BIOS, but not usually for ISP supplied routers as those tend to be "locked down".

Works for me using http://196.168.1.1 but not just 192.168.1.1 without the http:// - but I am Windows 7.

iirc, 7 or 8 years ago either worked with an older version of Firefox that I was using on my EeePC NetBook that I had a Netbook derivative of Ubuntu running on. I haven't used that device on my LAN in recent years though, so I don't know about Firefox in that regard any newer than Firefox 2.0; anything newer version of Firefox would run at all, missing "libraries" and such.

Yep as 196.168.0.1 is the other common one I have encountered over the years and Belkin may use 196.168.2.1

WestEnd said

By default routers uses 192.168.1.1 as the main line to the router and if you changed it or someone else changed it then whom ever did the change needs to fix it. As of now all router regardless for Consumers are 192.168.1.1 to access them-if different then you need to contact the manufacture for support on their router.

You may have only used some routers from one or two brands that had 192.168.1.1 as default however that does not mean all brands and models use the same.

Not sure why you think 192.168.1.254 is not a valid IP used by routers/modems when quite a few brands do. ex: https://www.lifewire.com/192-168-1-254-818386

I have a Netgear router in use that can be accessed with either 10.0.0.1 or 192.168.0.107 (may be due to the Cisco modem/router using the 192.168.0.1) for example.

Depending on the router you may be able to change the default IP to access it.

Since you use Linux if your PC is connected directly to the specific router you are trying to access you could use a Terminal to help.

For example typing in say netstat -r or ip route | grep default

Should give you your gateway IP to router.

This is the output of the suggested CLI commands. As I keep saying the IP is NOT in Question it is the failure of fiire fox to access the address. Nmap -sP and ping both report it connected. as an ex-teacher can I respectfully ask the people who insist on telling me the Ip is wrong-PLEASE READ THE QUESTION

netstat -r 

Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface default dsldevice.lan 0.0.0.0 UG 0 0 0 wlp2s0 link-local * 255.255.0.0 U 0 0 0 wlp2s0 192.168.1.0 * 255.255.255.0 U 0 0 0 wlp2s0

ip route | grep default

default via 192.168.1.254 dev wlp2s0 proto static metric 600

Red face very much in evidence!!

I should have thought of it sooner ...but.... I have just turned the router off and on again ------ Normal contact has been restored. Unfortunately I am at a loss still as to the cause of the original problem.

Thanks to all - even those who wished to change my router address Best wishes R.