"One reason to use your Tomato-enabled wireless router as a
client is to bring wireless access to a wired peripheral. For
example, suppose you have a gaming console, such as an Xbox or a
networked printer, which only have a wired Ethernet connection.
Using a wireless router in reverse ("client mode"), you can connect
to the Xbox and/or printer, and have the freedom to place them
anywhere you want (well, anywhere the router can pick up the source
signal, of course).
"Another way to use a router in client mode is to extend a
wireless network. For example, suppose your primary wireless router
is on an upstairs floor, but your laptop can't pick up the signal
when downstairs. Connecting your downstairs PC to a router in
client mode may let you pull in that distant signal, especially if
you outfit the router with more a powerful antenna.
"Technically, when in client mode, your router can only pass the
incoming wireless signal to clients connected to one of the
router's LAN ports. To re-broadcast the signal wirelessly, the
router would need to be configured as a
repeater—unfortunately, Tomato does not yet support repeater
mode. One option is to switch to DD-WRT V24, which does support
repeater mode, although it is in general not as user-friendly as
Tomato. Another option is to use two wireless routers--one
configured in Tomato client mode, connected by Ethernet to the
second router, configured as an AP (access point)."