Two NICs - same gateway

fourhead · Posted: Tue Sep 06, 2005 8:38 pm Post subject: Two NICs - same gateway

Hello, I have two NICs in a computer, and I've edited /etc/conf.d/net to assign two P addresses to those NICS like this:

iface_eth0="192.168.1.1 ..."
iface_eth1="192.168.1.2 ..."

Now, I want both NICs to use the same default gateway, but whatever I try, the gateway won't be set. I tried:

gateway=192.168.1.10"
routes_eth0="default via 192.168.1.10"
gateway_eth0="192.168.1.10"
gateway="eth0/192.168.1.10"

Those where all the possibilities I found in this forum - but they all don't work. What am I doing wrong here? Oh, I copied the net.eth0 init script to net.eth1 of course and have them both in the default runlevel.

Tom

NeddySeagoon · Posted: Tue Sep 06, 2005 9:00 pm Post subject:

fourhead,

What do you really want to do?
You cannot have two NICs on the same subnet, apart from a few special cases, none of which involve pointing them at the same gateway.
_________________
Regards,

NeddySeagoon

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

fourhead · Posted: Tue Sep 06, 2005 9:07 pm Post subject:

To be honest, I have no idea. I have installed a Gentoo Samba server for a friend of my parents in his office, which all works fine, and I'm administering this server via SSH because it's in another city. Now there's some other computer guy who for some reason has installed an extra gigabit NIC in this computer to connect it to a second Windows server, although there's absolutely no need for such a connection. Believe me, I have NO idea what this should be good for, this guy is kinda strange, but I just have this problem that Gentoo wouldn't assign the gateways correctly.

Tom

NeddySeagoon · Posted: Tue Sep 06, 2005 9:47 pm Post subject:

fourhead,

You can only have one defualt gateway. Thats the route that matches all the packets that are left over when all the other routing rules have been applied.
If you add an extra on manually (you can) on ly the first on in the routing table will be used because there will be no packets to send of econd and subsequent default gateways.

You need an admin policy if you are sharing admin with another person, so you both know what state the system is it at any time.

You may have other gateways to other network segments like this

fourhead · Posted: Wed Sep 07, 2005 7:44 am Post subject:

No, now I cleared up with this guy what he wants to do. He wants to connect the two servers to a gigabit switch, although I tried to explain him that it makes no sense when 1. all clients have only fast ethernet and 2. the two servers don't have to transfer any data betweeen them, but ok. Now he first wants to have both NICs because he for some reason thinks that he can't connect the computers when he removes the 100mbit nic and uses only the 1000mbit nic - well.

Tom

NeddySeagoon · Posted: Wed Sep 07, 2005 4:22 pm Post subject:

fourhead,

The 1000Mbit NIC will fall back to 100Mbit if needed.
If the switch is 1000Mbit capable ans so is the switch, then the server to switch should run at 1000Mb and switch to client at 100Mbit. The switch will do buffering and rate changing.

That should mean that when the network is busy transferring data from server to clients, each client sees a better data transfer rate. However ... should the 1000Mbit NIC be fitted to a 33MHz, 32bit PCI bus then the PCI bus limit will be reached first. Also if data is being read/written to a single drive, it cannot provide data fast enough to max out the PCI bus or the NIC.

In short, unless you have a server with a 64 bit 66MHz PCI bus and a RAID disk setup, a 1000Mbit NIC is a waste of money, since the bottleneck has now been moved to another part of the system with a very small increase in throughput.
_________________
Regards,

NeddySeagoon

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