2 NIC problem - Please Help

sudeep333 · External Since: Mar 06, 2009 Posts: 1

Hello to all the masters,

I am using RHEL 5 and facing problem related to 2 NICs.

NIC1 is connected to the internet and used to provide the internet
access to all my internal LAN systems which are connected to my second
NIC2 via a hub.

NIC1 is on DHCP and i am providing static IP address on NIC2 -
192.168.0.1

My LAN systems are pinging to my server but not able to provide
internet access to my LAN. My LAN systems are on windows XP

Please tell me what should i do.

NIC1 Configuration
DHCP

NIC2 Configuration
IP: 192.168.0.1
Mask: 255.255.255.0
gateway:

i have edited the /etc/sysctl.conf ipv4_forwarding to 1 but still the
issue is there.

Please tell me that is there anything related to iptables or any
simple solution is there.

My need is just to provide the internet access to my LAN systems via
my server.

Thanx in anticipation

Jan Gerrit Kootstra · External Since: Apr 08, 2004 Posts: 295

sudeep333 schreef:
> Hello to all the masters,
>
> I am using RHEL 5 and facing problem related to 2 NICs.
>
> NIC1 is connected to the internet and used to provide the internet
> access to all my internal LAN systems which are connected to my second
> NIC2 via a hub.
>
> NIC1 is on DHCP and i am providing static IP address on NIC2 -
> 192.168.0.1
>
> My LAN systems are pinging to my server but not able to provide
> internet access to my LAN. My LAN systems are on windows XP
>
> Please tell me what should i do.
>
>
> NIC1 Configuration
> DHCP
>
>
> NIC2 Configuration
> IP: 192.168.0.1
> Mask: 255.255.255.0
> gateway:
>
> i have edited the /etc/sysctl.conf ipv4_forwarding to 1 but still the
> issue is there.
>
> Please tell me that is there anything related to iptables or any
> simple solution is there.
>
> My need is just to provide the internet access to my LAN systems via
> my server.
>
> Thanx in anticipation

Sudeep,

It has to do with Iptables.

Just look for Linux firewall howto on Google and you find some good
examples.

Kind regards,

Jan Gerrit Kootstra

H.Janssen · External Since: Mar 08, 2009 Posts: 1

Dear sudeep333,

sudeep333 wrote:

> Hello to all the masters,
>
> I am using RHEL 5 and facing problem related to 2 NICs.
>
> NIC1 is connected to the internet and used to provide the internet
> access to all my internal LAN systems which are connected to my second
> NIC2 via a hub.
>
> NIC1 is on DHCP and i am providing static IP address on NIC2 -
> 192.168.0.1
>
> My LAN systems are pinging to my server but not able to provide
> internet access to my LAN. My LAN systems are on windows XP
>
> Please tell me what should i do.
>
>
> NIC1 Configuration
> DHCP
>
>
> NIC2 Configuration
> IP: 192.168.0.1
> Mask: 255.255.255.0
> gateway:
>
> i have edited the /etc/sysctl.conf ipv4_forwarding to 1 but still the
> issue is there.
>
> Please tell me that is there anything related to iptables or any
> simple solution is there.
>
> My need is just to provide the internet access to my LAN systems via
> my server.
>
> Thanx in anticipation

Yes, this is partly OK. Your system is able to do routing, and if you define
the server as default gateway on the XP boxes, packets will probably go out
to the internet, and never come back, because your 192.168.0 subnet is,
completely correct, a private subnet, and cannot be routed back

Just one iptables line will do the job:

/sbin/iptables -t nat -A POSTROUTING -o eth0 -s 192.168.0.0/24 -j
MASQUERADE

and all traffic from your clients will go out as originating from the
server.

The XP clients should have the server as default gateway and the same DNS
settings as your server in /etc/resolv.conf.
You could consider to use "dnsmasq" as DHCP and DNS server to set
all parameters in the clients automatically.

Good luck!

H.Janssen
Alkmaar