The Mother Board

I am trying to connect a newish computer (Windows 7) with only an RJ45 socket to a network of older computers (XP and 2000) which are all on a 10 base 2 ethernet chain. Yes... coax connectors! The question is, can I use both the BNC and RJ45 sockets on the same network card at the same time?

Welcome to Motherboards.org.
You cannot directly connect a coax to a LAN (rj45). There are matching transformers (adapters) that do that job.
They are available from http://www.newegg.com/ and other sources.
With most coax links, each is dedicated to a specific IP address on a machine. The IP administrator and you need to chat as to setting up on the system.
If the system has provision for rj45 (Cat5e), that use is preferred over the coax. Not advisable to connect both.
http://www.thenetworkencyclopedia.com/entry/10base2/

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Oops sorry I didn't make my post very clear. The Windows 7 computer would have to connect through a hub to the RJ45 socket on a computer which is attached to the 10 base 2 cable. All the LAN cards on that particular network have both BNC and RJ45 sockets. The BNC sockets are in use for the 10 base 2 cable, but I want to know if I can plug an RJ45 into a card that already has a cable plugged into the BNC port, so both ports on the card are in use at the same time. Will these cards (3COM 3C900 Combi and RTL8029AS types) allow these two ports to be used simultaneously?

Sorry, that last question was a little bit unnecessary as it had effectively already been answered. I decided to use a second network adapter on the same machine and have now connected an RJ45 cable to both PCs (which are numbered PC1 and PC3) through a small hub. The sockets on the hub light up, indicating that the hub is working and has detected a connection to both computers. The ethernet adapter on PC1 (Windows XP) is set up with the IP address 192.168.100.1. I have set up PC3 (Windows 7) as 192.168.0.3. I went through the network setup program on PC3 and set it up on WORGROUP, so it should be able to connect to the other computers also on the WORKGROUP. However, neither computer can connect to the other. I have attached a jpg image of PC3 showing as much information as I can about the error.

Each node or terminus on a coax setup is intended for one computer. You could use the RJ45 connection to a small hub or router, and then use two computers on that node. But each requires a unique IP address.
For ease of setup, all computers must be part of the same named workgroup. And each computer has its own unique IP address, such as 123.456.789.XXX. The last one to three digits give each computer its unique address.
For connection solely between two computers, a crossover LAN cable is the only means. For connection to a hub and several computers, standard through-put LAN cables are used. Between hubs or routers, a crossover LAN cable is required, unless the hub or router has a crossover switch for port 0.
Check that the firewall on both computers is set to fully trust each other.
http://www.cisco.com/c/en/us/support/do ... hbase.html

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F@H.. to solve mankind's maladies.. in our lifetimes!

The Windows XP computer (PC1) has two separate ethernet adapters... one onboard and the other on a PCI card. The PCI card connects to a BNC plug on a coax chain to other computers, and uses the IP address 192.168.0.1. The RJ45 is plugged into the other (onboard) ethernet controller, which has the IP address 192.168.100.1. The RJ45 cable is connected to a hub, which appears to be in working order.

Also connected to the hub is another 10 base T lead which connects to the onboard ethernet controller on the Windows 7 PC (PC3), which has the IP address 192.168.0.3. Both sockets on the hub are lit up to indicate they have a connection. The RJ45 ethernet sockets on both computers are also lit, indicating that the cables are connecting properly. However, PC3 cannot see any network. Neither computer can ping the other, although they can both ping their own IP addresses and 127.0.0.1.

The CMD window on PC3 says "Media disconnected". As the cable is connected from both computers to the hub, I don't understand what this means. It also says Transmit failure. The only network PC3 picks up is "Unidentified network", which contains only PC3!

Diagnostics has failed to find the error. Troubleshooting the ethernet controller gives the time-worn phrase "This device is working properly".

No, that is not possible.

Your other mistake is you are trying to put a computer with the wrong network address in the network.

Since PC1 has a 192.168.100.x address on the RJ45, PC3 should have a 192.168.100.x address as well. You need to configure PC1 as a router so PC3 knows where to go for the rest of the world. I think the easiest and quickest way would be to use ICS on PC1 and make the coax connection the "WAN/internet" port in that configuration.

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