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Multihomed setup

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Paul Primmer
Occasional Visitor

Multihomed setup

I am trying to set up a Multihomed configuration. I have a 6100 notebook running Win2K which comes with two NICs built in. One is a 10/100 wired NIC and the other is a 802.11b wireless. I'm connecting the 6100 wireless NIC in an 802.11b AdHoc network to a 567 Jornada using a wirless 802.11b card. I've configured the 6100 wireless NIC with an IP address of 192.168.1.1 and the Jornada has an address of 192.168.1.2. These two devices talk to each other and I can synch. using Microsoft ActiveSync. What I am having trouble doing is from the Jornada going out the other NIC card on the 6100 which is connected to the network. This wired LAN has an IP of 15.65.83.10, subnetmask 255.255.255.248 and Gateway of 15.65.83.9. This would be helpful to get working as the 6100 could act as an access point for my Jornada.
3 REPLIES
Mark Fenton
Esteemed Contributor

Re: Multihomed setup

In the windows 2000 networking setup, you'll have to turn on ip forwarding.

The default setup for "internet connection sharing" uses a 192.168.0.x addressing scheme -- which if you're not too set on the .1.x scheme you're using now, would probably be the easiest way to go.

Share the wireless (sets the address to 192.168.0.1) and then you'll be routing packets out to the hard-wired nic.

((there's pretty decent help available on the Microsoft Knowledge base web-site -- ICS))

hth

Mark
Paul Primmer
Occasional Visitor

Re: Multihomed setup

Thanks for the speedy reply. I understand the 192.168.0.x part but I wasn't sure where to go to start IP forwarding in windows 2000. On some notes from Microsoft they indicated that you did this by modifying a value in the registry (which I did) but that didn't change anything so I hope changing the IP addresses will work.
Ron Kinner
Honored Contributor
Solution

Re: Multihomed setup

Contrary to popular belief you do not need to fill in the gateway on your second NIC. In fact, it usually won't work. The Default gateway tells it where to send a packet if it doesn't have a specific route to that network. If you have two it just confuses the issue. How to choose which to take? Generally it will take the one which appears at the top of a route print (the 0.0.0.0 means default gateway).

What you do is pick the gateway that goes to the most places. Say you have one which goes to the internet. That one better have the default gateway because it is impossible to add that many static routes. The other one will usually only go somewhere locally and will have access to a limited number of subnets so that one will not need a gateway. Instead you add a static route
route add a.b.c.0 mask 255.255.255.0 d.e.f.g -p
for each network a.b.c.0 that can be reached through gateway d.e.f.g.

Forget about having two links to the internet. Unless you can run a bgp routing protocol you can only use one link at a time.

In order to use your PC as an IP forwarder you will have to tell the other devices that they can reach a certain network by going through your box. This probably requires adding routes to them which point to your box as the gateway though if they are both running RIP you could also run RIP and that would tell the other boxes that you can get them to different networks. You can also fake it somewhat with NAT. See
http://www.microsoft.com/WINDOWS2000/en/professional/help/HowTo_share_conn.htm

Ron