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Old 06-26-2010, 05:11 AM   #1
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Question Suse Linux server having 1 NIC and connected to 2 ISP router

The system is quite simple:

a. One SUSE Linux Enterprise Server 10 (x86_64) server
b. The server has a single private static IP address of with subnet and using the gateway (the local IP address of the router).
c. The LAN cable is then connected to a switch and the switch connected to a router that connects to an ISP while at the same time the router provides IP forwarding to the local IP of the server. The server now gets internet connection from the router and local users are connected to the switch to locally access the server.
d. This is the setup now and it is working flawlessly.

What I need to accomplish:

Connect a 2nd router (again with IP forwarding to the existing local IP of the server) to the switch wherein this 2nd router is connected to the internet via a different ISP so that external users can SIMULTANEOUSLY access the server from ANY of the two ISP. Obviously, a second gateway must be added or defined in the server so that it routes information from/to server to the 2nd router. The local IP of the 2nd router is and I suppose this will be the gateway to be defined or added in the server.

The problem:

How to add the 2nd gateway in the server configuration? This link - provides the actual screencapture of the settings to be modified.

I suppose I should be using "expert configuration" to do this but you see I'm no expert at all. Can you kindly assist me on how, what and where to put the modifications pls?

Kind Regards,
Lex Roxas
Old 06-27-2010, 09:40 AM   #2
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Location: DaeJeon,Korea
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Sorry for my poor english...

I recommand you to contact with possible engineer who may from ISP or switch provider.
Because this is not a common network structure,
In common sense, to coexist 2 or more network area at one place, one system require which to aggregate net-info and to control them.

In your case two net-area meet at one point what is switch.
This means the switch is the core of network information exchange(NIX)

Abscent of switch's routing setting means that abscent of dynamic NIX then all system must have static routing info and manual control to update them.
(exactly this is not perfect answer. if all indivisual system running dynamic routing protocol such as RIP,
then each of them can commucanate with router and themselves.
then can accomplish NIX dynamically without setup switch...
This mechanism may possible but may contains much unveiled troublesome.

So regardless of your custom demand and unmentioned circumstance, three or more inter-net area recommanded to be configured to have different private net-class which remove none-unicast traffic cross reference(sorry...this is not general english description but i don't know how)

This is not a part of indivisual linux system but consepts of network structure.
I think so...
I recommand you to meet someone who can advise to you or setup switch function.

I'm learning english but stll have much trouble to communicate.
"콩글리쉬 작열이군"

Last edited by ggeagle; 06-27-2010 at 10:16 AM.
Old 06-28-2010, 09:55 AM   #3
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Distribution: Debian 6+, CentOS 5+
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If I understand correctly, you want to have two separate routers which connect to two separate ISPs and then have the server be able to get out to the Internet through either. If this is the case you just need to add an additional route in the kernel routing table for default route. Now if you want to do load balancing or some other advanced features you would need a hardware router that support 2 or more WAN connections, or you will need to write some iptables rules to forward traffic appropriately. As far as forwarding the request to the internal server from the new router that will be done within the routers configuration. It is easiest to add a new default route to your routing table form the Command line.

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface   *        U     0      0        0 eth1     *        U     0      0        0 eth0
default         UG    0      0        0 eth1
default         UG    0      0        0 eth0
as you can see route will show you the servers current routing table to add another default route run
route add default gw eth0
here is a page with all sorts of information on routing tables


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