CentOS - Jun 2010 - Dual personality Server (network pass through)

I have 3 nics in a NATed gateway file server. Two nics (eth1, eth2)
provide dhcp and nfs services to an internal subnet via a dedicated
switch. The other nic (eth0) connects to an external WAN switch to
provide net access to the systems in the subnet.

                               --- eth1
WAN switch eth0 --- |               SUBNET switch
                               --- eth2

Question:
Is it possible to disable the NATing, nfs, dhcp and just somehow
bridge the external WAN nic to the internal ones such that it's just a
pass through? Basically having the server behave like a switch?
Allowing the internal systems to join the network on the WAN. I know
how to disable NAT, nfs and dhcp but not how to configure the nics.

I know I could simply unplug eth1, eth2 from the server and plug them
into the WAN switch but my goal is to script this so I don't have to
physically plug and unplug network cables each time.

Thanks

-- 
Robert Arkiletian
Eric Hamber Secondary, Vancouver, Canada

2010/6/15 Robert Arkiletian <robark at gmail.com>:
> I have 3 nics in a NATed gateway file server. Two nics (eth1, eth2)
> provide dhcp and nfs services to an internal subnet via a dedicated
> switch. The other nic (eth0) connects to an external WAN switch to
> provide net access to the systems in the subnet.
>
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? --- eth1
> WAN switch eth0 --- | ? ? ? ? ? ? ? SUBNET switch
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? --- eth2
>
> Question:
> Is it possible to disable the NATing, nfs, dhcp and just somehow
> bridge the external WAN nic to the internal ones such that it's just a
> pass through? Basically having the server behave like a switch?
> Allowing the internal systems to join the network on the WAN. I know
> how to disable NAT, nfs and dhcp but not how to configure the nics.
>
> I know I could simply unplug eth1, eth2 from the server and plug them
> into the WAN switch but my goal is to script this so I don't have to
> physically plug and unplug network cables each time.
Just create network bridge:
http://www.cyberciti.biz/faq/rhel-linux-kvm-virtualization-bridged-networking-with-libvirt/



--
Eero

On Monday, June 14, 2010, Robert Arkiletian <robark at gmail.com>
wrote:
> I have 3 nics in a NATed gateway file server. Two nics (eth1, eth2)
> Is it possible to disable the NATing, nfs, dhcp and just somehow
> bridge the external WAN nic to the internal ones such that it's just a
> pass through? Basically having the server behave like a switch?
> Allowing the internal systems to join the network on the WAN. I know
> how to disable NAT, nfs and dhcp but not how to configure the nics.
> 
You do this by creating a bridge.

The Red Hat/CentOS way is to create emptyish interface files like:

# cat /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
BOOTPROTO=none
BRIDGE=br0
ONBOOT=YES

# cat /etc/sysconfig/network-scripts/ifcfg-eth1
DEVICE=eth1
BOOTPROTO=none
BRIDGE=br0
ONBOOT=YES

And then a bridge interface file:

# cat /etc/sysconfig/network-scripts/ifcfg-br0 
DEVICE=br0
TYPE=Bridge
ONBOOT=yes
STP=on
IPADDR=system.ip.address.here
NETMASK=your.dotted.quad.mask

Obviously, adjust as needed to match your actual hardware, etc.

This can of course also be scripted using the actual networking commands, 
that I don't recall offhand.

-- 
"No animals were harmed in the recording of this episode. We tried but that
damn monkey was just too fast."