I found today my older router "FritzBox" (Fon Wlan 7390). I searched the web for some things i could do with my router, then I found that I can use it with my new newer "Fritzbox" and use the old as an repeater. So plugged in the electricity and a lan cable. After it booted up, I found out the router ip using /ipconfig. But as I try to connect to the interface, by browser says "Connection refused". I can ping my router with no loss. Somebody had the same issue?
I used the "emergency IP" that is universal to access the router.
Link where I found my solution.(german) https://avm.de/service/fritzbox/fritzbox-7390/wissensdatenbank/publication/show/374_Benutzeroberflaeche-im-IP-Client-bzw-WLAN-Repeater-Betrieb-aufrufen-wenn-IP-Adresse-unbekannt/
Do you know the model of the router?
Usual first step in these situations are a reset of the router like @bigchris has said i dont know of any routers which dont include a reset button off the top of my head.
By the sounds of connection refused you have disabled local access to the router i once did that on a draytek and had to restart the configuration because there is no way of accessing it locally. Its a slim chance but you may have remote access on the router enable so you could try and find the WAN address and access it that way.
I have found this thread from a couple of years ago with the same problem.
it does appear that you need to find an analog touch-tone phone and plug it into the RJ11 (telephone) port on the device and dial those keys to reset it to factory default if you do not have the password (the manual states that it cannot be recovered without factory reset).
credit to @gravyface
2 interface via "emergency IP"preparations
Disconnect all network cables from the LAN ports of the FRITZ! Box.
Press the WLAN button on the FRITZ! Box to turn off the WLAN radio network.
The wireless LED starts blinking. Once the WLAN LED goes out, the WLAN radio network is turned off.
Connect a computer via a network cable to a LAN port of the FRITZ! Box.
Call FRITZ! Box
Call the connected with the FRITZ! Box computer on the Internet browser's address 169.254.1.1 on.
If the user interface of the FRITZ! Box does not display:
Assign the network adapter that is connected to the FRITZ! Box, the IP address 169.254.1.2 .
Call the connected with the FRITZ! Box computer on the Internet browser again, >the address 169.254.1.1 on.
What I did and It worked is to change the static IP address on the device you're trying to access to. Also, make sure the port to the device is used. For example, you change 10.0.0.1 to 10.0.0.2. If it's still not working, try changing it again. The port number is default to be 80, however, it can be different. If different for example http port is 81, you can simply have the address to be 10.0.0.1:81.
Have a good day.