Allied Telesis AT-S39 - Manual (Page 180)

Section III: Web Browser Management
180
Gateway address
This parameter specifies the default router’s IP address. This
address is required if you intend to remotely manage the switch
from a management station that is separated from the switch by
a router.
4. After you have set the parameters, click Apply. Your changes are not
stored by the switch until you select Apply.
5. If you made a change to the IP address, subnet mask, or gateway
address, you must reset the switch to activate your change. You
cannot reset a switch from a web browser management session. You
can reset a switch from a local or a Telnet session, or by using the
Reset button on the switch.