Multilink loadbalancing

[royalblues]

I would like to know how the multilink will behave if i have 3 links bundled together each of diffrent bandwidth.

Eg. i ahve 2 links of 1MB each and the 3rd link is a 512K link

I have been using multilink without any problems with same bandwidth links but it doesn't seem to work properly in the above scenario.

i would like to know how the links will be load balanced in the above scenario.

Is this methos recommended?

thanks

Narayan

[The_guroo_2]

narayan

can u plz explain little bit more which routing protocol are you using and what short of router do u have.....????

[royalblues]

i have 3825 routers at both ends and iam not running any routing protocol.

all the routes are static routes.

Narayan

[The_guroo_2]

narayan

what sort of WAN link do u have and is it going to same destination or different.....like two isp's???? or same dest

[mpenning]

This depends on a lot of things, but let's assume for sake of argument that you are running 2800 series routers and thus have a recent IOS image. As long as you have set your bandwidth statements on the interfaces correctly, this should be supported.

If this doesn't help, posting more details like the type of router, IOS version, and configuration snip would be helpful.

[network.king]

Hi Narayan,

Traffic across the links in a multilink should get equally loadbalanced as the packets are equally fragmented across each link rather than each packet on each link .

I think BW factor comes into affect when we use some routing protocols and as you are using static routing , it should not have problem , might be some ios bug kind of thing or a new ios feature.

regards

vanesh k

[royalblues]

i think i need to rephrase the question.

say i have 2 links each of one MB bundled together and the traffic is 80%. The traffic is perfectly loadbalanced.

Now say if i add another link to the bandle whose capacity is just 128K, how the traffic will be loadbalanced here.

Will the traffic be loadbalanced between all the 3 links till the traffic exceeds 128K on the 3rd pipe and then distributes the remaining on the other links?

iam using 3835 routers with a 12.4 image (no routing protocols, & ofcourse since iam doing multilink it will be do the same destination)

Regards

Narayan

[globalnettech]

Hello Narayan,

when you do load balancing based on static routes (and CEF), adding a third link with lesser speed will cause that link to be equally utilised. The default for load-balancing is per-destination, you could change that to per-packet load-balancing, but that still would cause a bottleneck on the 128K link.

In order to use all 3 links, you would need a routing protocol such as EIGRP, which can do unequal cost load balancing.

How do you have your load-balancing configured now ? Can you post the config of your router ?

Regards,

GNT

[royalblues]

Hi GNT

The configs are simple

The Bandwidth is restricted on the Mux to 128K on the 3rd pipe.

interface multilink 1

ip address 10.10.10.1 255.255.255.252

ppp multilink

ppp multilink group 1

int serial 0/0

bandwidth 1024

encap ppp

ppp multilink

ppp multilink group 1

int serial 0/1

bandwidth 1024

encap ppp

ppp multilink

ppp multilink group 1

int serial 0/2

bandwidth 128k

encap ppp

ppp multilink

ppp multilink group 1

ip route x.x.x.x x.x.x.x 10.10.10.2 (other side multilink)

Narayan

[vladrac-ccna]

Hey Narayan,

I understood your question, and I dont think any of the previous posts answered it.

I'm looking forward to this answer as well,

Vlad

[rafaelgarcia]

Hi,

If you are looking for a multilink solution based on bandwidth you can take a look at the Gateway Load Balancing Protocol (GLBP). This protocol offer different options to handle traffic as well as offers redundancy for your links.

I have it implemented on a lab enviroment and it works very nice.

Let me know if it helps.

[royalblues]

Rafael

I know how GLBP works. THe post was meant to understand the behaviour of multilink when configured with different speed links.

As VLAD has already stated none of the posts have answered my question and the above post too deviates fron the original post.

Narayan

[network.king]

Hi Narayan,

As mentioned earlier , Traffic in a multilink is equally fragmented across the links and there is no per packet load sharing across the links .

So , even with the BW configured differently traffic would be distributed equally and if link capacity is less when compared with others , there would be drops and it would in turn affect others as the packets are fragemented equally across the links.

regards

vanesh k

[royalblues]

That is what i was exactly looking for. Whether packets will get dropped once the threshold is reached.

Can you give me any link that confirms the same

Thanks

Narayan

[network.king]

Hi Narayan,

I tried searching the net , but Iam not able to find the exact doc .

I have experienced the same kind of problem with one of our customer.

regards

vanesh k