Scenario: It's late, I need a switch, don't have one, but I do have a
moldy old forgotten Belkin router sitting in a drawer.

CURRENT STATE
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Primary router (R1): Linksys BF..something-whatever
R1 admin page: 192.168.2.1
No DHCP
My IP: 192.168.2.10
Secondary router (R2) to use as switch: Belkin-model-whatever

TO USE R2 AS A SWITCH
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1. Connect directly to any R2 LAN port, go to admin page 192.168.2.1
2. Disable DHCP
3. Set to use as "Access Point." AP mode bypasses all routing and
firewall functions. Set IP to 192.168.2.254. AP mode allows
connecting a regular CAT5 cable (versus crossover) from R1 to the WAN
port. Otherwise we'd have to use a x-over cable fm R1 to one of the
LAN ports.
4. Connect regular cable fm R1 to WAN port of R2.
5. R2 now acts as a switch, with all 4 LAN ports available for use. To
get to R2 admin page again, go to 192.168.2.254.

Yay.