3Com 3C840 User Manual page 201

If the remote site administrator provided a remote IP address and
I
netmask, select Specified and type in that address and netmask.
If the OfficeConnect Remote 840 is learning the remote IP address
I
from the remote site (PPP only), select Learn From Remote.
In order to have the remote site you are configuring act as the default
I
gateway, check the Use Remote as Default Gateway checkbox.
(Only one remote site can be designated as the default gateway.)
If you want to run RIP, select from the pull-down menu to have the RIP
I
set to Broadcast, Listen, or Broadcast & Listen, and if one of these
is chosen, set the RIP option to RIPV1 or RIPV2.
Ensure that Enable IP is checked (enabled).
I
4 Press the Next button to proceed to the IP Advanced Modify screen
(shown below).
5 Check the Enable PAT button to use Port Address Translation. (See the
Configuration Planning Table in Chapter 1 of the Installation Guide to
determine if PAT is to be enabled.) If Network Address translation is
required, select NAT.
Instructions for Telecommuting / Remote Office Access E-11