hi, I am sure this topic must have been discussed sevaral times.
- i have ordered 2 internet T1 (nxT1)with AT&T. The router at my end is 3640 (with two T1 ports modules) and want to use both T1s in loadbalanced way. I want to know how to configure at my end and what i need to tell provider? We have our own external IP block.
There are several options to achieve load balancing over nxT1. The options include multilink PPP (MPPP), multiple static routes, and dynamic routing protocol. The choice of the best solution is somewhat dependent on how AT&T has set up the nxT1. Assuming that the nxT1 terminates on a single router on your end and terminates on a single router on AT&T, then I would suggest that the optimum solution is multilink PPP. This will provide the most equal distribution of traffic over each link and will automatically adjust to failure of any individual link within the bundle.
If MPPP is not an option (or you choose not to implement MPPP) then I believe that multiple static routes would be the next most desirable solution..
Depending on what AT&T has provisioned it may also be possible to configure a dynamic routing protocol on the nxT1.
Have you asked AT&T for their advice about what to do? They know the details of how the connection was provisioned and what the available options are.
HI Rick, Thanks for the prompt and detailed reply. I have asked ATT about same questions that you had suggested. By the way do you have any good cisco link for configuring MPPP. Also do i need to enable/disable cef feature?
Please find the URL below for all info on MPPP... both theory and configurations ....
Hope this helps.. all the best..
You need to create one logical interface "multilink 1", configuration will be like this:
description MULTILINK 1
ip address x.x.x.x 255.255.255.252
no cdp enable
ppp multilink group 1
no clns route-cache
Similarly, configuration on serial interfaces will be like this :
description " "
no ip address
ppp multilink group 1
Remote end will also have similar configuration, Wan ip is to be assigned to multilink interface.
Thanks all for helping here.
I have received two WAN IPs from my provider for two T1s. With Multilink configuration, how to use them?
If you configure MPPP you would use only a single IP address. If the provider has given you 2 addresses they did not have in mind using MPPP.
If you do agree with the provider to configure the links as MPPP you would use only the one address and the provider could take back the other address.
If the provider gave you 2 addresses they expected the links to operate separately. You could configure the 2 links each with an IP address and you could then configure load sharing and redundancy with static routes or with dynamic routing, depending on what the provider will support.
I think you should opt for two separate links instead of using them as multilink. Because if one of the link have errors it will effect the performance of other link in MPPP and both link will become unusable. Load balancing can be done with seprate links also with redundancy.
IF i want to loadbalance with static routes, what is the preffered cofig? Should i have two equal distance static route to both link interface and have ip cef command or there is few more things to consider?
HOw does normally provider do loadbalace config on their side? (they have to consider routing my IP block loadbalacing on two circuits).
While I do not manage the router, we do have a 3xT1 connection with AT&T, and they use three different IP addresses for these serial lines. When I get my weekly utilization reports, one for each serial line, they are pretty much identical. On the rare occasion that we have trouble with one of the lines, the overall effect in not that noticeable to users. Also, when one line was being service, we still have the use of the other two. I am sorry that I cannot help with the actual router config, but I thought you might be interested to know about our setup in general terms.
yes you can have loadbalancing using the static or default route with same AD on each static or default route... but for that you are using the all the ip address in your case two ip address...
so benifit of usind Multilink ppp is to use only single ip address for the virtual multilink interface and you can make your other interface the member of the same multilink ppp... and then you can have single static router or default route pointing to the Multilink interface and you can have good load balancing,,,
in static router you donot need to deal with more configuration...
Mark and Devang , thanks for your thoughtful and informative reply.
Devang, yes you are right on that MPPP could be more desirable config. I might have to go with the way my provider - ATT suggests.
Probably the most important thing to consider is what your provider suggests. They do this kind of thing LOTS and they know best what works the best with their network. If the provider suggests MPPP then I think that you certainly should plan to do this. And if for some reason they suggest not to use MPPP then you should plan to use the serial links separately.
If ATT is your provider, I know that they do suggest MPPP for at least some of their customers. And depending on how the serial links were ordered and provisioned, sometimes they suggest to use them separately.
So yes, you should discuss this with ATT and you should take whatever suggestion that they give you.