10 replies to this topic

[crp]

I have had this problem now in 3 different distros but not with Win2008 , so i'm thinking the problem is on my end.

Goal: 2 NIC on same pc, listening to different ip addresses within the same network space. Gateway for each may or may not be different. Both NIC's functional at same time.

   On the Win2008 I have 2 NIC's , 192.168.1.55 and 192.168.1.235 . No problems in having routers route to each one and no problems in doing outbound traffic. In addition, on an older pc I have one NIC dealing with 2 different ip addresses, also with no problems or issues handling outbound or inbound traffic.

The linux boxes , however , trouble. I have tried ip forwarding on and off. same gateway and different gateways. The packets keep on getting lost, both incoming and outgoing. it is like the system does not know how to maintain a conversation on one NIC.
I figure this has to be do-able ; after all its how a firewall would work. So what is the 'trick' I am missing?

[V.T. Eric Layton]

This isn't even anything that I've ever remotely considered attempting. Hence, I don't think I have much knowledge/advice to offer you.

[LilBambi]

I assume you mean Windows Server 2008? Yes, and as long as the two nics meet Windows Server 2008 requirements for the name/model of allowable nics, you are good to go.

Here's something that might help:

Configuring Multiple Default Routes in Linux

Quote

Assume you have a Linux system with more than one network interface card (NIC) — say eth0 and eth1. By default, administrators can define a single, default route (on eth0). However, if you receive traffic (i.e., ICMP pings) on eth1, the return traffic will go out eth0 by default.

This can be a bit of a problem — especially when the two NICs share the same parent network and you’re trying to preserve sane traffic flows. In a nutshell, this post will explain how you can ensure traffic going into eth0 goes out only on eth0, as well as enforce all traffic going into eth1 goes out only on eth1.

You’ve found the one post that actually explains this issue; your googling has paid off. You wouldn’t believe how many advanced Linux routing websites out there explain how to route everything including your kitchen sink — yet fail to clearly explain something as simple as this.

As always, we’ll explain by example. Assume the following:

    eth0 - 10.10.70.38 netmask 255.255.255.0
    eth0's gateway is: 10.10.70.254
    eth1 - 192.168.7.126 netmask 255.255.255.0
    eth1's gateway is: 192.168.7.1

First, you’ll need to make sure your Linux kernel has support for “policy routing” enabled. (As a reference, I’m using a v2.6.13-gentoo-r5 kernel.)

From reading over the rest of that posting you will find that part of the problem, like my Jim found out with FreeBSD years ago, is that you need to build your own custom kernel to do this sort of thing.

This article explains all that is needed.

Hope that is what you are looking for.

The references he uses in the article are:

Quote

References:
[1] http://www.policyrouting.org
[2] http://www.linuxhori...o/iproute2.html
Update: Here are some additional resources, that I have found useful.
http://lartc.org/how...iple-links.html
http://linux-ip.net/...ing-tables.html
Update: Apparently, OpenBSD also now supports multiple default routes through a new feature called the Virtual Routing Table:
http://www.packetmis...-routing-table/

I would read his article though. It's an excellent piece!

[crp]

LilBambi, on 03 August 2012 - 03:42 PM, said:

I assume you mean Windows Server 2008? Yes, and as long as the two nics meet Windows Server 2008 requirements for the name/model of allowable nics, you are good to go.
Here's something that might help:

Configuring Multiple Default Routes in Linux

I wonder if that post holds a WordPress record . It was created in Nov 2007 and is still getting active , non-troll/spam, comments!

My basic reaction is - oh my friggin' gosh - why is something so simple in the Windows world so hard in the linux world? I'm not compiling kernels or anything like that. However, there was a link mentioned that deems following up on
http://sysadminsjour...routing-centos/

[LilBambi]

Quote

In prior versions, you had to setup some custom scripts, but that’s no longer the case - all the hooks are there in the OS now. In this example, imagine a CentOS host with two nics. 192.168.0.2/24 is on eth0, and 10.0.0.2/24 is on eth1. The default gateway is set to 192.168.0.1. Any host accessing 10.0.0.2 from any subnet that isn’t on 10.0.0.0/24 will have it’s reply packets sent out via 192.168.0.1. Some firewalls drop this type of traffic cough Cisco ASA’s cough. Thanks to the iproute2 package in Linux, this is easy enough to fix.

Apparently, that older 2007 posting is superceded by the 2009 one LOL!

This one looks much easier too.

I knew it could be done in Linux, but never needed it myself.

[crp]

LilBambi, on 07 August 2012 - 04:02 PM, said:

Apparently, that older 2007 posting is superceded by the 2009 one LOL!
This one looks much easier too.
I knew it could be done in Linux, but never needed it myself.

I think it only applies to CentOS. and it still involves installing iproute2 . I'm really puzzled why something so easy to do in msWindows is such a pain in the linux world. Does the Apple variant of linux have a hard time with it as well?

[LilBambi]

But at least now you don't need to compile a kernel.

As far as Apple, no idea. Can't afford their PowerMac Desktops which is the only place you could use two nics.

[Temmu]

crp, what are you trying to accomplish with 2 nics on the same network?
bandwidth-improvement?
prolly not routing as that has an interface on each of 2 networks, not the same network...

and...
did you get it resolved?
my limited experience w/iptables reminds me how quickly one can break networking altogether!

[crp]

2 totally separate incoming ISP

no resolution, if it can not be done as simply as msWindows can do it, I can not introduce complexity to the linux boxes.

[Urmas]

http://chris.olstrom...setup-dual-wan/

[LilBambi]

Do you want to aggregate the two ISP connections?

10.4. Multiple Connections to the Internet

If not, then you want true DUAL WANS, and Urmas has your answer!