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Community Member

Load balancing to different ISP's

Hello

I have two T1 lines to two different ISP's. I was wondering if there is a way that could allow me to load balance accross the two T1 interfaces. I am not able to use BGP although I dont think that BGP would help me much. The the two ISP's have givven me two completly different subnets. Am I able to use equal cost default routes to my ISP's? Is there a command like the "backup interface" command or any other commands for this purpose?

I have looked every where with no solution, I would be delighted if someone could help me out.

Thanks .

1 ACCEPTED SOLUTION

Accepted Solutions
Gold

Re: Load balancing to different ISP's

Yes, this is the way it should work. I would think that balancing your outbound traffic, and then directing your inbound traffic based on the somewhat balanced outbound traffic, might do a pretty good job at getting the load sharing pretty consistent inbound, but I don't know for certain. It would really depend on your traffic mixes, and other factors.

:-)

Russ.W

9 REPLIES

Re: Load balancing to different ISP's

Without BGP you're pretty much out of luck unless you can get the two ISP's to cooperate, which is not very likely...

The only way I can think of "balancing" is to put the hosts you want to use one T1 on one subnet and the others on the other one, not very efficient on your LAN.

Why isn't BGP an option? If you went with BGP it would be very simple to do load balancing...

Community Member

Re: Load balancing to different ISP's

Thanks for your reply

The situation I have is that I have Internet connection from these two providers. Currently we have implemented the option that you have stated. Although I cannot use BGP I was wondering how that would be possible?. Correct me if I am wrong but you would have to exept full routes from two providers witch is not a good option.

How about using default 0.0.0.0 route to these providers with the same metric then giving the next hop the address of the apropriate ISP. you would have load balancing and redundancy.This would couse per packet load sharing or with CEF per source-destination load sharing. Ofcource this is just an idea, would it work? I have EIGRP as my routing protocol.It seems Foundry networks have released a device that can do load balancing from diffrent ISP's.

I would be glad if you could help me out.

Gold

Re: Load balancing to different ISP's

Are you nat'ing the address spaces you've been given by the two different ISP's? I'll assume so.... There are two seperate problems here, the inbound traffic flow and the outbound traffic flow. It's easy enough to load share your outbound traffic using static defaults--the inbound is where you are going to find you have little to no influence over things. If you are nat'ing your traffic, the outbound load sharing placing the source address in two different address pools might get you some of the load sharing inbound you are looking for, but I'm not certain how much.

Other than this, if you're really after "better" inbound load sharing, you're going to need BGP, and you'll probably need to work with your providers some. You can do some level of inbound traffic adjust using as path prepend, but the fact is that inbound load sharing is, altogether, rather problematic, since you aren't in ultimate control of the routes or the policies of your service providers, or their upstreams.

As for someone releasing a product that promises perfect load balancing--well, I know two things. First, I'd rather not have out of order packets, even if that messes up my perfect 50/50 traffic split. And I know that controlling inbound load sharing is problematic, because of the way the Internet is built. With one service provider, you have a good bit of control, with two, it's much much harder to get things to split evenly, if you can do it at all.

:-)

Russ.W

Community Member

Re: Load balancing to different ISP's

Hi

Thanks for you reply

I am natting. I was thinking that if I could send out a users traffic out an interface after natting to the range of IP's that I have been given by the apropriate ISP's, with using CEF (souce-destination or per destination) what would happen would be that my users would be balanced between these interfaces and to the internet from both lines, witch would gives outgoing load balancing and redundancy. The incoming traffic would come from the same line that the user first sent the first traffic. This would be because of the source IP address change to the one that the apropriate ISP have givven me.

If one line goes down (using default routes to next hop) the other will still be working but carries all my users to the internet.

I hope that my comments would get my idea across.

I have not tested it. I would be glad to see what you think.

Thanks again.

Gold

Re: Load balancing to different ISP's

Yes, this is the way it should work. I would think that balancing your outbound traffic, and then directing your inbound traffic based on the somewhat balanced outbound traffic, might do a pretty good job at getting the load sharing pretty consistent inbound, but I don't know for certain. It would really depend on your traffic mixes, and other factors.

:-)

Russ.W

Community Member

Re: Load balancing to different ISP's

Thanks

Community Member

Re: Load balancing to different ISP's

I have a similar setup, but my 2 ISP's are on a multihost WAN. How could one setup CEF to work across 2 sites that all additional sites have dual 512k DLCI's into and then GLR'd to a PIX at both sites? (Am I stuck going the BGP route?)

Right now, I just point half the group to one ISP and the rest to the other with default routes. (Not very efficient)

The design plan is to have the sites be failover for each other and loadbalance outbound traffic. There is a T1 between the 2 sites with the ISP links. The ISP links are both T1's as well.

Thanks

Mike

Gold

Re: Load balancing to different ISP's

I'm not certain I understand your setup (?).... Are you saying all the sites connect directly to the internet independantly, or through your main site, or (?).

Russ.W

Community Member

Re: Load balancing to different ISP's

If you want to avoid BGP altogether, you might want to look at load-balancing boxes that base their operations on DNS.

But again, for proper route control, BGP is the way to go.

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