I have a server (running server 2003) with two dual NICs. I have four separate physical networks connected to the server. In my Network connections I have the four connections and a loopback adapter - all connected. I can only ping IPs on two of the networks at a time.

For example: if I have all of the network connections enabled then I can only ping IPs on network 1 and 3. If I disable network 1, then I can ping IPs on networks 2 and 3, etc. So my NICs are OK and my physical connections are OK.

Can I have four separate networks working at the same time on one computer? Can anyone help me?:confused:

Yep, but 4 separate networks will need 4 NIC's otherwise you will be changing IP's all the time.

I have to ask, what are you trying to do with this setup as it seems overly complex ?

I am in a large production plant with separate networks in each mill. I have devices on each of the networks that I would like to access with one server. So I put four NIC's in the server and linked one to each network. Problem is, only 2 work at a time.

Check your subnets, mask and default gateway
For example have
Mill 1 on 192.168.1.x
Mill 2 on 192.168.2.x
Mill 3 on 192.168.3.x
Mill 4 on 192.168.4.x
all with a subnet mask of 255.255.0.0
ALL connections should have the same default gateway e.g. 192.168.0.1

This will make your job a hell of a lot easier.

All of my subnet masks are 255.255.248.0. Is this OK?

To keep things nice and simple, especially as you are running a private network, stick to 255.255.0.0
It gives more usable addresses then you'll need, but I'd rather have too many than not enough.

A mask of 255.255.0.0 will give useable addresses of 192.168.0.0 - 192.168.255.255

Also check the settings on NIC 1 as there maybe something amiss them.

Also using subnets you shouldn't need to have all 4 networks connected directly to your server.
Throw in a router (default gateway possibly) to connect them and then connect the server to the router.

Lets start over before you go down a rat-hole here. The reason why you can only ping from two of them has to do with where your computer thinks the ping response needs to leave from. You might be receiving the PING OK but the response is leaving on a different NIC and therefore would never reach its destination and the result is that you think you have connectivity problems when in fact you have an asymmetric paths due to misconfigured network paths.

Why don't you provide a quick explanation of what each of the network's IP addresses/subnets are. This will determine how to configure your 4-NIC computer or even if there is a better way to connect to all 4 networks. A router will not work if all of your networks fall in the same subnet.

OK.
Network 1: IP-172.27.40.0-255
Network 2: IP-172.27.45.0-255
Network 3: IP-172.27.8.0-255
Network 4: IP-172.27.49.0-255
Also, my Loopback adapter,
Connection 5: IP-172.27.0.1
The Subnet masks are all 255.255.248.0
All Gateways are the same.

Does this help?:(

Ok, tell me what your gateway(s) that you are using are. In the meantime, here is what you have for networks because of the mask that you are using:

Range 1: 172.27.40.0 - 172.27.47.255
Range 2: 172.27.8.0 - 172.27.15.255
Range 3: 172.27.48.0 - 172.27.55.255

If I assume that you typo'd the address of Network3 and you meant to say .48. Instead of .8. then ignore Range2. You only have two ranges of IP's that you're using and thus only 2 Networks. If you really mean .8. then it doesn't matter the solution below is still correct. If I further assume when you say "all gateways are the same" to mean that you have 172.27.40.1, 172.27.45.1, 172.27.48.1, and 172.27.49.1 as gateways then this now makes perfect sense why you experienced only two cards at any given time talking to one another.

Basically your Network1 and 2 are really part of the same network. Your Network3 & 4 are also part of another network. You don't have 4 networks. So you had asymmetric routing and your pings will behave exactly like you mentioned below.

What you need to do is the following at the very least:

1) Resolve the Network overlap between all of your subnets. I'm not sure why you chose 255.255.248.0 as a network mask but you need to do one of two things to resolve the overlap.

a) You either re mask everything on all of your devices to have 255.255.255.0 subnet mask:

- 172.27.40.0/255.255.255.0 (172.27.40.0 - 172.27.40.255)
- 172.27.45.0/255.255.255.0 (172.27.45.0 - 172.27.45.255)
- 172.27.48.0/255.255.255.0 (172.27.48.0 - 172.27.48.255)
- 172.27.49.0/255.255.255.0 (172.27.49.0 - 172.27.49.255)

OR

b) re-IP all of your devices into these networks:

- 172.27.40.0/255.255.248.0 (172.27.40.0 through 172.27.47.255)
- 172.27.48.0/255.255.248.0 (172.27.48.0 through 172.27.55.255)
- 172.27.56.0/255.255.248.0 (172.27.56.0 through 172.27.63.255)
- 172.27.64.0/255.255.248.0 (127.27.64.0 through 172.27.71.255)

I think
Option a is easier to deal with and makes more sense to most people.

2) Get rid of all of the gateways you defined. You don't need the gateway(s) to be able to communicate with any of the networks. You only need a gateway when you want to communicate with an IP address that is NOT directly connected to your network (i.e. something on the Internet). So if one of those networks above has a router that gets you on the Internet then you only need to put that router's IP address as a default gateway on your 4-NIC computer in order for your 4-NIC computer to reach the Internet. Otherwise if you don't want your 4-NIC computer to reach the Internet then just don't add any gateways to it.

Casey

I changed the IPs of our networks (no thanks to my IT department). Thanks to all for your help - you guys are awsome!

I mean awesome...