When two routers are used at home or in a small office, two separate layers of address translation can occur. This situation is especially confusing in incoming connection and device discovery.
Basic approach
Translates NAT addresses and, in some uses, ports. If the WAN side of the second router receives a private address from the first router, the clients may be on different local networks. The failure of a device to discover the printer in another room while internet access is running may be related to this structure.
Application steps
- Show the LAN and WAN addresses of each router in a table.
- Determine which device is doing DHCP and routing.
- If a single network is desired, consider the manufacturer's access point or bridge mode guidelines; Do not change the setting randomly.
Practical example
If the first device distributes 192.168.1.0/24 and the second device distributes 192.168.2.0/24, the computer connected to the second network can access the Internet, but multicast discovery on the first network may not work as you expect. This does not directly indicate that the printer is faulty.
Interpret the result correctly
Switching to bridge mode may interrupt internet and management access. Do not make unplanned changes over a remote connection. If keeping the two networks separate is a conscious design, the solution is not to combine them but to define the necessary access with control.
Source and follow-up reading
Protocol or command details: RFC 3022. The steps and example scenario are IPScans editorial narrative.