Should me computer, router and router range expander all have the same IP Address?

They may not have the same IP address. IP addresses must be unique.

Isn’t the router the one that assigns all the (internal) IP addresses to everything?

It’s the DHCP server, which the router may be configured to become.

Ah.

There should be no duplication of IP addresses in your active network. However, each device must be in the same IP address range, otherwise those that are duplicate are bound to have connectivity issues. For example: Your router has an IP of 192.168.1.1 therefore, all other devices must have the IP format of 192.168.1.# (# being unique number in the range of 2 to 254)

njnyjobs. I am having trouble connecting to the internet after the new router install. THe router IP address under the internet connection area is 25. range all of the computers I am trying to connect to the internet are 192. range. Does the routers internet access IP need to be a 192. range also?