There are two products you may need in addition to what you have now to 
setup an internal or external async remote bridge.   

NetWare Async Remote Bridge software    905-301974-001  $395/network
WNIM+ hardware                          905-302029-001  $895/board
 
You have two decisions to make:
 
1.  WNIM+ hardware vs. COM1/COM2.  The WNIM+ is a 4-port "smart" card (it
has an on-board processor).  Compared to the COM1 port that (probably) came
with the server the WNIM+ will off-load the main CPU, leaving more time for
file service.  COM1/COM2 can support 9600 bps; WNIM+ 19.2kbps on all 4
lines.  The WNIM+ also offers more ports.
 
2.  Internal (in a file server) vs. External (in a workstation) bridge.
Here you're trading off performance for the need to have another machine.
Except for ELS II, a WNIM+ is strongly recommended for an internal bridge
(maximum of 1 WNIM+). An external bridge can support either COM1/COM2 or
WNIM+.  The external bridge can support 2 WNIM+ boards.
 
The WNIM+ drivers are in the async remote bridge package mentioned at top.
The COM1/COM2 drivers are shipped in all NetWare 2.1 and above.  NetWare
2.0a users can use the software in the async remote bridge package for an
external bridge.  The software will not work in a 2.0a internal bridge.
IOW, everything you need for an external bridge is in the above software
package for either 2.0a or 2.1.  WNIM+ drivers for 2.1 internal bridge are
also included.

Caveat:  Neither the COM1/COM2 nor the WNIM+ drivers today support dial-up
modems at greater than 2400 bps.  Using leased line modems at up to 19.2
kbps works great, however.
   
-- Skip Addison
   Communication Products
   Novell