Load balancing with 2 links

Hi friends,

I want to configure 2 512 kbps links on the same router. Can anyone tell me how to configure 2 links in such a way that if one links fail other link will take the responsibility.

We have cisco 3600 series router & my boss wants load balancing to be configured for both the links We don't have cisco's load balancer. So I think with the access-list I can decide which ip addresses can reach to internet through which interface. So I think I need to configured static/manual load balancing. Can it be possible to configure dynamic load balancing without load balancer.

One more, I want to use the 2nd link to be used as a backup link for 1st one. So how can I configure it, I thought I will use HSRP but it will work only when one of the 2 routers fail. I want backup for the link.

Can anyone help me regarding these issues.

Thanking all of you in advance.

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Comments

networker050184

I want to configure 2 512 kbps links on the same router. Can anyone tell me how to configure 2 links in such a way that if one links fail other link will take the responsibility.

Do you wan the other link to be a back up (only when the first link fails) or are you trying to equaly load balance them?

So I think with the access-list I can decide which ip addresses can reach to internet through which interface.

For this you are going to need to use ploicy based routing to se the nest hop for the source traffic.

Are you using BGP to connect to an ISP or is this internal using an IGP?

stone123

If it is possible then I would like equal load balancing. Last option is to configure manual load balancing in such a way suppose 20 hosts are present then 10 host will use 1 link & 10 will use other one. But I want to ensure that If 1 link fails then all 20 hosts will use backup link. We are not using BGP, we have default route pointing to ISP.

We have cisco 2811 router.

networker050184

You can add static defualt routes (pointing to the other side of your link) as a Cisco router will by default load balance over two eaqual cost paths. With default settings this will load balance on a per destination basis. If you want your ISP to equally distribute traffic back to you you will have to get with them about that as your configuration will not influence the incoming traffic. Are both the links to the same ISP?

dtlokee

Why not use something like MPP? What encapsulation type are you using?

stone123

We have 2 different ISP's. I am thinking of using cisco's OER. But I am not sure about it.

dtlokee

stone123 wrote:

We have 2 different ISP's. I am thinking of using cisco's OER. But I am not sure about it.

The only "true" way to do this then is to BGP tables from the providers to determine the best path to each destination, then use identity NAT to translate to the appropiate IP addresses depending on the provider. Any other solution will result in suboptimal routing, but based on the 3600 you have you won't be able to pull a full routing table from the providers, so static routing is the most likely solution but this will result in some suboptimal routing.

I have not deployed OER yet, but it is not for load balancing.

networker050184

If you are connected to two ISPs you should look into BGP as dtlokee stated. Default routes wouldn't be able to find optimal routes through either ISP. You may end up going a longer path through one ISP to something that may only be one path away from the other ISP.

stone123

BGP Tables will do, but I am worried about the resources that protocol of the internet will consume. I will run out of memory very soon.

Paul Boz

Can't you just run GLBP? GLBP load balances as well as provides for failover in case one of your links goes down. I'm not sure if you can run GLBP on just one router and I can't lab it at the moment but it's worth looking in to.

APA

stone123 wrote:

One more, I want to use the 2nd link to be used as a backup link for 1st one. So how can I configure it, I thought I will use HSRP but it will work only when one of the 2 routers fail. I want backup for the link.

Can anyone help me regarding these issues.

Thanking all of you in advance.

Just an FYI.......

You can configure load balancing a.k.a load sharing with HSRP..... and utilize both links at the same time..... Just configure each router to be a standby router for the other.... so you would have 2 standby groups on each router.....

Paul Boz

Using two standby HSRP groups is an interesting way to do it. There are lots of great suggestions in here.

dtlokee

GLBP and HSRP are available on LAN interfaces but in this case he's tryig to load balance to multiple service providers and GLBP or HSRP won't be an option. Static routes will work but they will result in sup-optimal routing.

networker050184

HSRP or GLBP would not be a viable option when connecting to two different IPS.

EDIT: dtlokee beat me to the punch....