Setup TCP/IP Routing

by Johannes Helmig [Published on 28 June 1998 / Last Updated on 28 June 1998]

I am using the following network to explain the setup requirements of Routing (assuming that you have knowledge of TCP/IP setup and on setting up systems with MULTIPLE network adapters):

Some of these systems are/can beWindows95/98, some are/MUST be NT4 / 2000.

System #1:
This system (can be Windows95/98 or NT4) has only 1 Network card and is configured (example is using NT4) :

This system knows about all systems on its own network cable (192.168.1.x) and will use the Gateway/Router 192.168.1.2 (which is System#2) for communications with any other system.

System#2:
This is a Windows NT4 system configure with 2 Network cards:
Network configuration, tab : Adapters :
- 1: a 3COM Etherlink III (3C609)
- 2: a Novell NE2000 Adapter



The first Network card communicates with System#1:
Network configuration, tab : Protocols
- Properties of TCP/IP
- selected Adapter : Novell NE2000
- selected radio button : Specify an IP Address
- IP-address: 192.168.1.2, Subnet Mask: 255.255.255.0
, no gateway address defined :


the second Network card communicates with System#3:
Network configuration, tab : Protocols
- Properties of TCP/IP
- selected Adapter : 3Com Etherlink III (3C509)
- selected radio button : Specify an IP Address
- IP-address: 192.168.2.10, Subnet Mask: 255.255.255.0
, no gateway address defined :


In addition, NT4 TCP/IP protocol must be configured to "route":


System#2 can communicate directly with System#1 and System#3, but NOT with System#4 (because it does NOT know about a network 192.168.3.x and how to reach it).

We need to help System#2 by giving some information, on how to get to System#4, by either defining System#3 as a Gateway or by manually manipulating the TCP/IP routing tables using the command-line utility ROUTE.
ROUTE.EXE is part of Windows95 and Windows NT4 and is documented in the Resource Kit:


You can get the same information by using a Command-Prompt window and
typing : "route /?" ( text-file of the output from an NT4 system )

In our example, we would enter on system#2:
ROUTE ADD 192.168.3.0 192.168.2.11
this informs System#2, that all communications for TCP/IP addresses 192.168.3.x(the '0' in the route-command translates to 'each system with an address 192.168.3.x', which in our example includes System#4) has to go via 192.168.2.11 ( which is System#3).

The rest of the Network is configured similar to Systems#1 and #2.

If you like more info on the ROUTE-command, please look at the following article in the Microsoft Knowledge Base:
http://support.microsoft.com/support/kb/articles/q158/4/74.asp


Test your setup using PING:
Example: from System#1 :

- command : "ping 192.168.1.2" getting a reply
- command : "ping 192.168.2.11" getting a reply

System#1 can communicate with System#2 and #3 in this test.

Example: from System#3

- command : "ping 192.168.2.10" getting a reply
- command : "ping 192.168.1.1" : message "Destination host unreachable"

System#3 can communicate with System #2, but NOT with System#1.
In such cases, check on ALL system the IP-addresses, Gateway-addresses and that IP-forwarding is enabled.

And don't forget: IT MUST WORK IN BOTH DIRECTIONS, otherwise the system receiving the PING-test-signal does NOT know on which route to send the echo back !


Browsing a system, which is accessed via a Router

Workgroups have limitations, and one of them is:
Systems on different network cables cannot be in the same workgroup !
To access a system via a router, you need to use the "Find"-command in the Windows
Start-bar and search for a "Computer" :


To avoid to get an Error-message : "The network name cannot be found" :

you need to create/update the file "LMHOSTS":

On Windows95/98, a sample-version called LMHOSTS.SAM is installed with TCP/IP in your Windows-directory. Rename/copy it to LMHOSTS and enter the IP-address with the computername. On Windows NT4/2000/XP, the files LMHOSTS and/or LMHOSTS.SAM
are located in "C:\<Windows-directory>\system32\drivers\etc".

Then you can "find" this system:


Now the big question: Can I use Windows95 as a Router ?

Officially: NO.
Microsoft has reserved the functionality to route for Windows NT.

Unofficially: YES, but with limits
I have not yet tested this myself, but have seen in the Newsgroups several postings, that it is possible

"
Want windows 95 to act as a router!
( http://gargoyle.apana.org.au/~nat )
using Windows95 as a TCP/IP Router between ONE Ethernet-cable and a Dialup Networking connection with a STATIC IP-address :

Apparently, you need the Dialup-Networking Upgrade 1.2, which includes a TCP/IP upgrade,
and then need to define in your Windows95 Registry:
key : [HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\MSTCP]
create a new sub-key "EnableRouting" , value (as StringValue): "1" :


I repeat: I have NOT tested this myself on Windows95 , and can therefor NOT ANSWER
any question on this topic.
I have tested this on Windows98SE, where it is working !

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