IPX (Internetwork Packet Exchange) is an older protocol - originally developed by Novell for Netware networks. A number of DOS games need to have an IPX peer-to-peer network configured in order to support head-to-head gaming.  In order to setup a minimal IPX DOS stack - you will need to download the following files:

ftp://ftp.symantec.com/public/english_us_canada/products/ghost/layers/LSL.ZIP
ftp://ftp.symantec.com/public/english_us_canada/products/ghost/layers/IPXODI.ZIP
Novc_300.zip from http://developer.intel.com/design/network/drivers/novc_300.htm

Once you have downloaded these files - you will need to unpack them all into a single directory on your DOS virtual machine.  You can then load the IPX network stack by running the following commands:

LSL
DC21X4
IPXODI

These commands need to be loaded in that exact order.  Once you have two virtual machines on the same network - you can confirm that IPX networking is working by downloading 'IPXCopy' (ftp://ftp.simtel.net/pub/simtelnet/msdos/lan/ipxcpy27.zip) and using it to copy a test file from one virtual machine to the other.

N.B. The two virtual machines can be on the same host computer, or on separate host computers.

If you want - you can unload the IPX stack by running:

IPXODI /U
DC21X4 /U
LSL /U

In exactly that order.  The nice thing about this is - if you have one program that you need IPX networking for - you can write a batch file that loads the IPX stack, runs the program, and then unloads the IPX stack automatically when you are done.

Cheers,
Ben