Greg Barniskis nalists at
Wed Jul 20 22:37:21 GMT 2005

Lowell Gilbert wrote:
> Don't top-post, please.
>>On 20 Jul 2005 09:38:22 -0400, Lowell Gilbert <
>>freebsd-questions-local at> wrote:
>>>Sushubh <sushubh at> writes:
>>>>I am going to install FreeBSD on a machine we plan to make a server.
>>>>Now, we have 2 lines of internet coming to our place through 2
>>>>separate lan modems. I want the server to take these 2 lines and
>>>>combine the speeds to form a single line which can be used by our lan
>>>>to access the internet.
>>>>I have got 3 lan cards on the linux machine. 2 for the incoming
>>>>connections from the 2 lan modems which have the gateways<>
>>>>and <>.
>>>>How do I go ahead with making my server a gateway offering combined
>>>>bandwidth to our lan?
>>>I'm not sure I understand your message, but:
>>>How do you do it with the Linux machine?
> Sushubh <sushubh at> writes:
>>their is a bridge software in linux which can do that...
> That doesn't do what you described.  That's just regular bridging, to
> connect two links into a single subnet.  FreeBSD can do that quite
> well (there's a whole chapter titled "bridging" in the FreeBSD
> Handbook), but it doesn't have anything to do with load balancing
> across the two links, which is what you said you were after.

I think Lowell is right; bridging is not routing and is not going to 
load balance your ISP links. Even if you figure out how to make 
FreeBSD route your outbound traffic as if the two lines were one, it 
cannot really work unless both lines go to the same ISP router and 
they cooperate with you. They'd have to configure their router to 
treat the two lines as one, to load balance your inbound traffic.

For example, we have multiple ISP links (one fiber optic and two T-1 
lines) all from the same ISP. The two T-1 lines are configured with 
load balancing to effectively form a combined 3 Mbps link (but this 
is done with Cisco IOS, not FreeBSD).

Even though they all go into the same router on our end, the two T-1 
lines cannot be load balanced with the fiber link because the fiber 
and T-1 lines end in two different ISP routers on the far side 
(actually in two different POPs). So, we just have the ISP router 
configured to use the fiber if it's up, or to use the combined T-1's 
if fiber goes down.

Greg Barniskis, Computer Systems Integrator
South Central Library System (SCLS)
Library Interchange Network (LINK)
<gregb at>, (608) 266-6348

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