Find routers in bridge mode on network

I have 3 routers on my network.

Only one does the actual routing, the other 2 act as "switches" and wireless access points. This was accomplished by disabling DHCP and changing the IP ranges, so none of the routers have conflicting address ranges.

A fairly lengthy cable in the network has gone bad and has limited my coection speed to 10Mb/s half duplex. Until I replace the cable, I want to disable auto negotiation and attempt to use 100Mb/s or 1000Mb/s link speeds. The "switch" (router) in question is in a difficult location to reach.

How would I figure out the IP addresses of these other two routers? I don't recall exactly what they were set to, but they are on class C networks.

I am ruing Fedora, so Linux commands would be helpful.