OT - Vista networking woes

Hi All,
I'm running Vista 32bit Home Premium, and I'm having trouble with my network connections. I have a Wi-fi connection to the outside world that works perfectly until I plug in the wired connection to my PLC network. They have completely different IP addresses; the wi-fi router uses DHCP to hand out addresses in the 150.168.1.xx range, and the wired connection uses DHCP to give addresses in the 192.168.11.xx range. When I plug in the wired connection, I'm still connected to the wi-fi access point; it gives me "local" access only. As soon as the wired connection is unplugged, the wi-fi connection again allows internet access.

I've tried re-ordering the order in which Windows accesses network resources (in Network and Sharing Center / Manage Network Connections) to no avail. It seems to make no difference. I remember this working in Windows XP just fine. Is this just another Microsoft/Vista screwup that I will have to live with until I upgrade to Win7? Google is of little help because of the broad application of the keywords.

Using IPCONFIG at the CMD Prompt, I can see that I get a default gateway on both connections; it just won't connect to the Internet via wi-fi with the wired connection hooked up... grrrr...



Thanks for any info,

rpoet

I think that you're right about the Default Gateway being the problem.

When your PC needs to get to the Internet, it needs to get to an address outside the local LAN, so it goes through the Default Gateway. But wait... there are two of them. Confusion leads to panic. Panic leads to indecision. Indecision leads to timeout.

I found some interesting reading about multihomed computers using the keywords "multiple default gateways Vista Home Premium" on the Microsoft knowledgebase.

http://windows.microsoft.com/en-US/windows7/Configuring-multiple-gateways-on-a-network

I've had a similar issue on my XP box... I end up switching back and forth between my WiFi (Internet) and Wired (automation system) connections. More proof I'm a machine guy and not a network guru.

I dealt with a similar issue with my laptop except my wired connected is to the corporate network (and therefore the internet) and my wireless connection is to the PLC network. I tried to type up a clear and concise explaination of what's probably happening below.

Disclaimer: the information below pertains to Windows XP but according to my limited research on Microsoft's site, Vista and 7 work basically the same way.

By default, Windows automatically assigns something called a metric to each network interface based on the connection speed. Higher connection speeds get lower metrics and lower metrics have priority when communicating with remote networks. (I'm not sure how Windows handles situations where the metrics are the same). Because your wired connection is probably a higher connection speed than your wireless connection, it gets a lower metric and all network traffic that is destined for remote networks tries to use that connection. If all your PLC traffic stays on the 192.168.11.xx network, you can do one of two things.

1. Delete the default gateway from your wired connection. The default gateway is only necessary when traffic is going to remote networks.
2. Manually change the metric on the connection that goes to the Internet to be lower than the PLC connection (this is what I did and it has worked fine ever since).

If some of your PLC traffic needs to be routed to other networks (addresses not in the 192.168.11.xx range), then you will probably need to set up some static routes as described in Ken's link.

This post is getting long enough, but if you can't figure out how to change your interface metric, let me know and I'll try to help you out.

Just for reference ...
http://social.answers.microsoft.com...g/thread/a8119435-e280-47d3-bf41-cf4a8fc6e2c0

http://support.microsoft.com/kb/299540/

Why use two different address ranges? Replace the wired Router with a switch or just use the wired Router as a switch. Then your Gateway address is the same whether wireless or wired. To use your Router as a switch, disable DHCP, don't have anything connected to the WAN port, instead connect one of the LAN ports to the Wireless Router. Don't guarantee that it will work but I have done similar things in the past.

Bryan

@BryanG - there could be lots of network architecture reasons why OP needs 2 networks.

Along the same lines of what you suggested, it could be viable to connect the networks with a router so that he can access both the Internet and PLC network via the same interface. This could require more equipment and know how.

I think OPs best bet is to work on the Windows metrics as suggested above.

Hi All,
Thanks for all your input. I'll look into those solutions and get back on what works or doesn't. To answer BryanG's question, I have two address ranges because the PLC network is controlled by a Buffalo Technologies router. That router is paired wirelessly with a second Buffalo router (set to bridge mode) that allows for wireless connection to one of the PLCs on the network. The reasons why it was done this way are long story, but it's stable and has surprisingly low latency. I am however connected to the PLC network with a wired connection to the router, as I only have one wi-fi adapter in my laptop.

I think Ken hit it on the head; both routers are giving default gateways. I'll try and see in I can get the PLC network router to stop giving a default gateway. I still need it to do DHCP to allow easy connection (either wireless or wired) for troubleshooting and programming, but without two default gateways, maybe Windoze will be better behaved.

Thanks!

rpoet

If you are using 150.x.x.x address on a private subnet, you'll have problems. 150.x.x.x is a routable address.