Well, I know how to use ifdown and ifup to switch from my wired to my wireless card......

but say I have a server up and running with two wired network cards. So far I haven't been able to get both my wireless and my wired on at the same time using DHCP. Can I do that with two network cards in Linux or not? I'm definitely gonna have two network cards in my next system and have them put into different routers to spread out traffic over two IPs and then choose which services I run on which IP.....but they both have to be over DHCP. Is that possible? THANKS!

I have a laptop that has a wireless and a wired PCMCIA cards in it, I have had both cards in and up at the same time. I run mandrake 9.1 on it and don't' have any problem, both are running DHCP to my firewall. My firewall box has two Ethernet cards in it, one running DHCP to my ISP and one that is my inside network with static config on it.

is your DHCP server your internal server/internet connection share? or are you trying to get two IPs from your ISP? It could be the way your DHCP server is configured.

It's my internal server/router. When I have my eth0 up and I try "ifup eth1", it comes back as saying "File already exists".

I can't have both up without that error Anything I can do?

ok, I think this indicates that the interface already got the ip from the DHCP server,

[root@localhost les]# ifup eth1
Determining IP information for eth1... done.
[root@localhost les]# ifup eth1
Determining IP information for eth1...SIOCADDRT: File exists
done.

so if you do ifconfig, you should see something lilke this

[root@localhost les]# ifconfig
eth0 Link encap:Ethernet HWaddr 00:50A:EB:6D:CF
inet addr:192.168.1.240 Bcast:192.168.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:29 errors:0 dropped:0 overruns:0 frame:0
TX packets:10 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:4545 (4.4 Kb) TX bytes:1296 (1.2 Kb)
Interrupt:11 Base address:0x4000

eth1 Link encap:Ethernet HWaddr 00:05:5D:F1:24:A5
inet addr:192.168.1.246 Bcast:192.168.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:500966 errors:0 dropped:0 overruns:0 frame:0
TX packets:451400 errors:2 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:229188599 (218.5 Mb) TX bytes:73032146 (69.6 Mb)
Interrupt:3 Base address:0x100

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:68775 errors:0 dropped:0 overruns:0 frame:0
TX packets:68775 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:5151974 (4.9 Mb) TX bytes:5151974 (4.9 Mb)


The thing to do is go to your server/router and ping each of the addresses that are listed to verify they are working. you can also to netstat -rn to look at your routing table, example follows

[root@localhost les]# netstat -rn
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 lo
0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth0
[root@localhost les]#

you will see that both interfacess are listed and what interface is your default gateway, the 0.0.0.0 network is default, as you can see mine is on eth0

Ahhh....ok, thanks!! I'll go check it out!