«

I have a task to connect 2 Linux servers using a cross-over cable (but
with a twist).


SWITCH
|
|
Server-A - [NIC-A1 , NIC-A2]
/
/
x-over cable
/
/
Server-B - [NIC-B1 , NIC-B2]



NIC-A1 is the only interface connected to a switch. I need to connect
Server-B to the same switch but have no more switch ports.

My idea (may be silly) is to run a x-over cable from NIC-A2 to NIC-B1
and thus be on the same VLAN as NIC-A1.
For this, I need to somehow internally bridge NIC-A1 and NIC-A2 so
when I run the x-over cable, NIC-B1 will be part of the same segment.
Then I can assign IP to NIC-B1 and have my L2 connection via Server-A.
Is this at all doable???

Thanks
Ron

unix <> wrote:
> I have a task to connect 2 Linux servers using a cross-over cable (but
> with a twist).
>
>
> SWITCH
> |
> |
> Server-A - [NIC-A1 , NIC-A2]
> /
> /
> x-over cable
> /
> /
> Server-B - [NIC-B1 , NIC-B2]
>
>
>
> NIC-A1 is the only interface connected to a switch. I need to connect
> Server-B to the same switch but have no more switch ports.
>
> My idea (may be silly) is to run a x-over cable from NIC-A2 to NIC-B1
> and thus be on the same VLAN as NIC-A1.
> For this, I need to somehow internally bridge NIC-A1 and NIC-A2 so
> when I run the x-over cable, NIC-B1 will be part of the same segment.
> Then I can assign IP to NIC-B1 and have my L2 connection via Server-A.
> Is this at all doable???
>
> Thanks
> Ron

Of course this is possible in Linux.
It can be debated whether it is a good idea to do this, but it is your
own decision.

On 29.02.2012 17:47, unix wrote:
>
> For this, I need to somehow internally bridge NIC-A1 and NIC-A2 so
> when I run the x-over cable, NIC-B1 will be part of the same segment.
> Then I can assign IP to NIC-B1 and have my L2 connection via Server-A.
> Is this at all doable???

Certainly. You'll need to create a bridge interface on server A and add
NIC-A1 and NIC-A2 to the bridge. Assuming NIC-A1 and NIC-A2 are called
eth0 and eth1 respectively:

modprobe bridge
brctl addbr br0
brctl addif br0 eth0
brctl addif br0 eth1

This assumes that your kernel has bridge support compiled as a module,
and that you have the bridge userspace tools installed (see
http://tldp.org/HOWTO/BRIDGE-STP-HOW...he-bridge.html).

The IP configuration on NIC-A1 must then be moved to the new bridge
interface (br0). Also, the commands above must be added to the startup
scripts of your Linux distribution.

On Feb 29, 1:34*pm, KR <kristian.rasmus...@broadpark.no.spam.com>
wrote:
> On 29.02.2012 17:47, unix wrote:
>
>
>
> > For this, I need to somehow internally bridge NIC-A1 and NIC-A2 so
> > when I run the x-over cable, NIC-B1 will be part of the same segment.
> > Then I can assign IP to NIC-B1 and have my L2 connection via Server-A.
> > Is this at all doable???
>
> Certainly. You'll need to create a bridge interface on server A and add
> NIC-A1 and NIC-A2 to the bridge. Assuming NIC-A1 and NIC-A2 are called
> eth0 and eth1 respectively:
>
> modprobe bridge
> brctl addbr br0
> brctl addif br0 eth0
> brctl addif br0 eth1
>
> This assumes that your kernel has bridge support compiled as a module,
> and that you have the bridge userspace tools installed (seehttp://tldp.org/HOWTO/BRIDGE-STP-HOWTO/set-up-the-bridge.html).
>
> The IP configuration on NIC-A1 must then be moved to the new bridge
> interface (br0). Also, the commands above must be added to the startup
> scripts of your Linux distribution.

THANKS! THAT WAS VERY HELPFULL! I'll try it.

On Feb 29, 1:34*pm, KR <kristian.rasmus...@broadpark.no.spam.com>
wrote:
> On 29.02.2012 17:47, unix wrote:
>
>
>
> > For this, I need to somehow internally bridge NIC-A1 and NIC-A2 so
> > when I run the x-over cable, NIC-B1 will be part of the same segment.
> > Then I can assign IP to NIC-B1 and have my L2 connection via Server-A.
> > Is this at all doable???
>
> Certainly. You'll need to create a bridge interface on server A and add
> NIC-A1 and NIC-A2 to the bridge. Assuming NIC-A1 and NIC-A2 are called
> eth0 and eth1 respectively:
>
> modprobe bridge
> brctl addbr br0
> brctl addif br0 eth0
> brctl addif br0 eth1
>
> This assumes that your kernel has bridge support compiled as a module,
> and that you have the bridge userspace tools installed (seehttp://tldp.org/HOWTO/BRIDGE-STP-HOWTO/set-up-the-bridge.html).
>
> The IP configuration on NIC-A1 must then be moved to the new bridge
> interface (br0). Also, the commands above must be added to the startup
> scripts of your Linux distribution.

I looked at this and it seems once you bridge NIC-A1 and NIC-A2 you
can't assign IPs to NIC-A1. I need NIC-A1 to be reachable via L3 still
and have another IP for NIC-B1 in the same subnet. Can be done ???

On 01.03.2012 19:30, unix wrote:
>
> I looked at this and it seems once you bridge NIC-A1 and NIC-A2 you
> can't assign IPs to NIC-A1. I need NIC-A1 to be reachable via L3 still
> and have another IP for NIC-B1 in the same subnet. Can be done ???

You can't IP addresses to interfaces enslaved under a bridge interface,
but the bridge interface can have any number of different IP addresses
assigned to aliases (br0:0, br0:1 etc).

BTW, you're in the wrong newsgroup.

On Thu, 01 Mar 2012 21:46:11 +0100, KR wrote:

> You can't IP addresses to interfaces enslaved under a bridge interface,
> but the bridge interface can have any number of different IP addresses
> assigned to aliases (br0:0, br0:1 etc).

Nitpicks:

- Yes you can assign IP adresses to enslaved interfaces and that does
work. It's even the default Xen bridge setup. Whether it's a good idea in
terms of clarity is debatable, but it does work.

- Aliases are a thing of the past, of the 2.2 kernel. They are supported
nowadays only for backward compatibility. Today you just assign multiple
addresses to the same interface.

HTH,
M4