Multiple Networks Howto ...

ckoeber · Apprentice Joined: 21 May 2007 Posts: 156

Hello,

I am sure this is simple but I can't figure this out. I added a network card to an existing Gentoo installation to have two in total. ETH1 is my new network card which is a Gigabit connection and ETH0 is my old network card with just an 100 Mbit connection.

I would like for the new network card (ETH1) to connect to a 10.10.50.X (class C) network which accesses out local LAN and the old network card (ETH0) to connect to a 10.10.60.x (class C) network which is a wireless network that does not communicate with the 10.10.50.X network. This network also has internet access, if that is important.

I am not sure what to do. Right now both interfaces get DHCP but I cannot ping either card or get network access.

Any help is appreciated.

NeddySeagoon · Posted: Thu Jun 17, 2010 8:29 pm Post subject:

ckoeber,

As you use DHCP on both subnets, your system will be confused.

If you look in the output of the route command, you will see you have two defualt routes, which is a bad thing.
You need to set up routing for the non default interface manually.

post the output of

ckoeber · Apprentice Joined: 21 May 2007 Posts: 156

NeddySeagoon · Posted: Thu Jun 17, 2010 9:14 pm Post subject:

ckoeber,

You probably want your default route to point towards the next hop to the internet, or you won't be able to reach the internet at all. Therouting table you posted should work as the only default rout that will be used in the one on eth0.

When the kernel has a packet to route, it matches its destination IP against each rule in turn, when a match is found, the packet is sent, as 0.0.0.0 matches all packets, any packet that gets to the first 0.0.0.0 is sent over eth0.

As you use DHCP, its a matter of chance which default route is set up first ... it depends on DHCP server response times.
Hence you need to only allow the right default route, or set it statically in the net file.

Communication between eth0 and eth1 depends on Packet Forwarding being enabled in the kernel and turned on in /proc.
Its off by default, which is what you want.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

ckoeber · Apprentice Joined: 21 May 2007 Posts: 156

ckoeber · Apprentice Joined: 21 May 2007 Posts: 156

OK, I made the changes but still no luck. The connections to the server on both interfaces are still sporadic and unreliable.

Here is my current /etc/conf.d/net file:

fancyladd · n00b Joined: 28 Jun 2010 Posts: 1

I'm not entirely sure what you are trying to do. Do you want a host from the 10.10.50.x network to be able to communicate with a host on the 10.10.60.x network? If so then NeddySeagoon is right and you need to enable packet forwarding on your Gentoo machine. Also the following routes in your routing table seem wrong to me:

10.10.50.0 10.10.50.1 255.255.255.0 UG 0 0 0 eth1

and

10.10.60.0 10.10.60.1 255.255.255.0 UG 0 0 0 eth0

If the Gentoo box has two interfaces, one in 10.10.50.x and the other in 10.10.60.x then you shouldn't add a route that sends all traffic for those two networks to another host (this is what your routing table is doing right now). For example, if you try and ping 10.10.50.2 from your Gentoo box it will send that packet to 10.10.50.1 which is probably not what you want. To fix this you should clean up /etc/conf.d/net. You can remove "10.10.60.0/24 via 10.10.60.1" and "10.10.50.0/24 via 10.10.50.1" for sure. This might solve your problem; however I'm not really sure what your problem is because you didn't explain how you tested this. Also what is 10.10.50.1 and 10.10.60.1? Are these two routers? Do you want your Gentoo box to be acting as a router between the two networks? If so then you will probably have to add some routes on the other hosts on both sides of each networks, or else use your Gentoo box as their default gateway. Perhaps you can include a little diagram so we can have a full understanding of your networks.