I'm trying to set up a SLIP link using a serial connection between two XP computers. This is to test some specialized communications hardware that only supports IP via SLIP.

As a starting point, I'm simply connecting the two computers with a null modem cable to verify the SLIP connection is working. I configured the Guest computer's SLIP connection following this guide.

I have not found a comparable guide for configuring the host side, but I tried to create a complementary procedure: Network Properties / New Connection / Set up an Advanced Connection / Connect Directly To Another Computer / Host / COM1 / {choose users} / {finish}. This results in a new section in Network Properties labeled "Incoming" which has an item named "Incoming Connections".

After connecting the null modem cable between computers, I can successfully connect from the guest computer to the host. The Guest machine shows "Connected" in Network Properties, and I see the IP address in IPCONFIG. However on the Host computer, the status of the "Incoming Connections" device remains as "No Devices Connected". There is no new IP address in IPCONFIG, and there is no new interface in ROUTE PRINT.

On the Host machine, under Connection Properties / Networking / TCP/IP / Properties, there is a "Incoming TCP/IP Properties" dialog. I have set this for "Specify TCP/IP addresses, and I gave a range of 10 IP addresses in the network. I checked "Allow Calling Computer to specify its own IP address", since per the PDF document (above) I specified an IP address (within this range of 10).

Both computers already have Ethernet networks on I tried setting the SLIP addresses in unused space on the network. I also set them to a completely different network: and Same result: SLIP connection from Guest seems to connect, Guest gets an IP, but there is no evidence of any connection on the Host machine (No IP address, no route)

An LED monitor on the serial line shows traffic from Guest to Host when attempting PING the host over the serial cable. All pings time out - there is no response from the Host.

I verified the serial connections by running terminals on both machines. The serial connection works fine. As an additional test, I reversed the host and guest roles. Again, the Host machine does not acknowledge an incoming connection, or assign an IP address.

Since there is no IP address on the host machine, I can't connect or PING across the SLIP link. What am I missing in this configuration for SLIP?


The answer is that XP does not support SLIP for incoming connections. See this article

If you set it up, it will seem to connect, but it won't work. I was trying to do something that was impossible, due to mis-interpreting instructions on setting up two machines for a SLIP connection.

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