networking with multiple nic's

Mandle · 11-10-2006, 11:08 PM

I've got 3 nic's installed running Slackware 10.2. When I did the install it asked for a nameserver and I said that I didn't want one. Mistake number one. I've specified my gateway as 192.168.0.1(roomates computer). It is running winxp with ICS enabled and routing fine to My winxp install. The uppermost nic is the one plugged into the crossover cable.(pci1) I cant even ping the gateway. My ip is set to 192.168.0.69(you can tell i've not gotten any in awhile

I'm going to install slack 11 once I get this fixed, but I need some help. (I need to get this fixed for my own personal sanity. This has happend to me a number of times, whenever I try to set up a static ip, and the only thing that reliably fixes it is a reinstall with dhcp enabled.) I dont want to reinstall just to setup dhcp. Thanks

Mandle · 11-10-2006, 11:23 PM

well, I guess I just need a point in the right direction. Not too sure how bad on the newb scale this ranks, but I'm getting somewhere. thanks

jschiwal · 11-10-2006, 11:56 PM

The default gateway address does need to be your roommates computer interface ( The one you connect to or that connects to the LAN. ) You can check this with the route command:
ex: /sbin/route. the last line should look like:
default 192.168.0.1 0.0.0.0 UG 0 0 0 eth0

Does ifcofig show that the NIC interface has an IP address? If so, then either you set it up manually or you have access to a DHCP server through your roommates computer. You can run "/usr/sbin/ifconfig eth0" to check if it does.

The first two lines of output should look similar to this:

Code:

eth0      Link encap:Ethernet  HWaddr 00:17:31:AB:78:A9
          inet addr:192.168.1.102  Bcast:192.168.1.127  Mask:255.255.255.128

Now I'm not certain how windows does network sharing. What is your roommates WAN side IP address? If it is someting like 192.168.0.xxx then there may be a problem because his two interfaces may be in the same subnet. I did something similar once where my desktop didn't have a wireless interface but my laptop did. So I used ip forwarding to gain access to the internet. Both computers were running SuSE Linux. I had the wireless device in the 192.168.1.0/255.255.255.128 subnet and my desktop, and printer were on the 192.168.128.0/255.255.255.0 subnet. If your roommate has an interface with an internet address ( not a private one like 192.168.xxx.xxx or 10.xxx.xxx.xxx, etc ) then there probably isn't a problem.

Another thing to look for is the nameserver addresses. If you are configuring your interface manually, then you may need to get those addresses from you roommate. ( He can get them in the device properties configuration, or by entering "ipconfig /all". These address are needed in /etc/resolv.conf. Take a look at your /etc/resolv.conf file and see if they are there. Using dhcp this will be filled in. One trick is to set up your computer first for dhcp and record your ISP's nameserver addresses. Then add those address to /etc/resolv.conf when you configure it for static addressing. Sometimes, if you want your computer to function as a server you will want a static address.

manishsingh4u · 11-11-2006, 07:13 AM

I would like to add a little bit to what "jschiwal" said.
If your linux machine is connecting to the LAN via eth0, your system's /etc/rc.d/rc.inet1.conf should have these lines.

Code:

# Config information for eth0:
IPADDR[0]="192.168.0.69"
NETMASK[0]="255.255.255.0"
USE_DHCP[0]=""
DHCP_HOSTNAME[0]=""

And for default gateway

Code:

# Default gateway IP address:
GATEWAY="192.168.0.1"

You can check which interface(s) is / are available by using

Code:

ifconfig -a

or

Code:

dmesg | grep eth

Now the /etc/resolv.conf should have appropriate domain and DNS entries. You can get these value by using the trick told by "jschiwal"

Code:

search yourIspDomain.com
nameserver XXX.XXX.XXX.XXX
nameserver XXX.XXX.XXX.XXX

Replace XXX.XXX.XXX.XXX with primary and secondary DNS IP Addresses.

Now try restarting the network using

Code:

/etc/rc.d/rc.inet1 restart

Mandle · 11-11-2006, 12:03 PM

well, I'm going to make assumptions here. Foremost that my nameserver should be 192.168.0.1. The windows box running ICS. Works with windows, and unless nix uses drastically different dns protocols this should work. Thanks and I'll post an update either later today or tomorow.

TigerOC · 11-11-2006, 03:46 PM

Quote:

Originally Posted by Mandle

I've got 3 nic's installed running Slackware 10.2.

Can you tell us why you need 3 nic's

Quote:

When I did the install it asked for a nameserver and I said that I didn't want one. Mistake number one. I've specified my gateway as 192.168.0.1(roomates computer). It is running winxp with ICS enabled and routing fine to My winxp install.

First important concept to understand is that an ip address is assigned to a n ethernet card and not a box. Following on this if you have 3 ethernet cards in one box they must all have different subnet ip addresses.
Some practical examples. Lets say that you route through your mates box at 192.168.0.1 then the ethernet card connected to it must also have an address on the same range eg 192.168.0.2. The second ethernet card could be assigned an address like 192.168.1.1 and the 3rd 192.168.2.1. Boxes connected via 192.168.1.1 should have addresses in the same range eg 192.168.1.2 and their gateway would be 192.168.1.1. The same would apply to the 3rd card. Now if you intend sharing the internet you need to implement ip-masquerading and forwarding and preferably use some iptables rules see http://mia.ece.uic.edu/~papers/WWW/iptables.html

jschiwal · 11-13-2006, 10:27 AM

The nameserver address should be the internet address. If the windows machine supplies a DHCP service, it may be supplied if your client is set up that way. If not, you can get that information from the windows macbine. These are the DNS servers that resolve internet address when you browse the internet.