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Dual NIC Network Problems

By webmaster ·
We have a strange problem...
10 PC's, Win '98, Windows Networking,
Dual NIC's, dual Switched hubs, 1 hub is connected to all PS'c and cable modem for internet and External VPN provided by cable co. (uses dynamic IP's, TCP/IP only), 2nd Hubis connected to static IP 56K frame relay for connection to State Computer systems. (PC's connect using proprietary ANCIENT software as well as standard Telnet access to additional devices on same static IP connection)

When any PC bootsup, all seems well, Static IP is in place, dynamic IP's are properly allocated. If you start internet connection, no problem, works fine. If you then start any app that should use the static side, they cannot connect.

If after booting, you start any of the static IP apps FIRST, they work fine but the Internet side cannot connect and the Dynamic IP is lost.)

We have installed ZoneAlarm Pro but this problem existed before.

Also, wierdest of all...sometimes, for a few minutes, both side will work great. Then one stops working. This only happens once in every 10 or so reboots.



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additional info

by webmaster In reply to Dual NIC Network Problems

We have added a couple of Windows ME systems and they react exactly the same.

Each PC can see all the others on the net but the external VPN is only acessable IF the internet side is currently working.

Each PC reacts independently, meaning there appears to be no negative inmteraction between PC's.

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Be in one subdomain at a time

by humble-bee In reply to Dual NIC Network Problems

It seems that your PC (Windows) can only handle being in one subdomain at a time -- either on the static side or on the dynamic side, whichever comes first! (Note: I'd assume that your static network and dynamic network belong to two different subdomains.)

I heard that you can assign two different IP addresses to a Windows PC to get the problem resolved. However, I have not had a chance to look into that for a solution. Maybe some other Winsdows guru out there know how to do it.

If youhave a Linux system, the solution is easier. The way you can assign a second IP address to a Linux box (with one NIC or dual NIC, doesn't mater) is as follows. Assuming your current IP is and you wanted to add the address to it, the command on a Linux box is simply:

ifconfig eth0:1

Again, assuming eth0 is your current network interface.

Hope that it helps.

Best Regards,

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Wholesale re-work?

by eBob In reply to Be in one subdomain at a ...

The problem you describe is really one of "routing". To me it makes sense to hand that work over to a system that is built to handle it, and to NOT rely on a PC O/S to do the work.

I would consider a wholesale re-work of the network.

Dump the dual-NIC nonsense. Bring all of your PCs back to a simple single-NIC setup. DHCP? Why not - it makes admin so much simpler (most of the time). These come back to a 100Mbps switch. Then get a "proper" router.

It will need 3 interfaces. The Ethernet link (assign it a fixed IP address from your internal network) will be the default gateway for all of your systems. One WAN interface will be to "State Computers". Either config a routing protocol, or setup some static routes so that when your users want to use those systems, their traffic is shuffled off in the right direction. The third interface connects to your ISP. It should be the gateway of last resort, so that all "other" (non-LAN and non-'State') traffic passes to the Internet.

Getting a router setup seems scary at first, but I guarantee that it's a whole lot simpler to manage than the 2-NIC setup you're working with.

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Good Solution.

by admin In reply to Wholesale re-work?

This works well. Personally, I like to use statics on private space internally because then I can chart each WS and look on the wall and instantly troubleshoot or fix something from my office, but that's pretty old school I suppose and not really necessary.

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Two networks, Two NICs

by thor In reply to Dual NIC Network Problems

I have the same problem. Adding broadband internet to existing networks, (Security being a big issue), we planned on using a second TCPIP network bound to the second NIC with the idea that Network "A" would be invisible to any security breech on Network "B".

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Real server and dual NIC

by JMK555 In reply to Dual NIC Network Problems

I recently installed a SBS (Small Business Server) network for about 10 users. SBS is based on Server 2000 and offers a nice bundle of products for the money. Mix of 98 and W2K Pro clients. The deal:
1) Cable modem to
2) Router to
3) #1 NIC (external use)
4) #2 NIC (internal use) runs to switch and LAN

This scenario runs a few $'s, but it can basically be done the same way with other OS and NOS. All traffic runs through the server/proxy which authenticates, allocates, and validates thetraffic inbound and out IF PROPERLY CONFIGURED. In addition to the gateway machine, I also use antivirus and software based firewalls on each workstation. Ok, so I am little over zealous. :)

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