Multichassis Multilink PPP

I've been reading up on MCMPP to try and answer a few of my questions. My biggest question right now pertains to the number of devices involved. Here's the setup. We have 5 different paths from one POP to another. 3 of these paths are T1s from a single provider; the other 2 are high-speed radio links. The radio links are the paths of last resort more or less (until we can get fiber in the ground).

We'd like to bond 2 of the T1s together to increase bandwidth for a specific voice application as well as isolate that traffic and increase redundancy. One of the ideas we had was in regards to MCMPP. Can we spread these 2 T1s out over 2 devices on either end (ie, a 2611xm and a

3660 at each POP)? Bonding them together on a single router on each end is trivial but we'd like to introduce more redundancy than that for this particular application. I haven't found anything that says I can have multiple devices on either end. I have however found numerous references to terminating circuits from a single device onto multiple destination devices. Make sense?

A1 B1 A2 B2


A1 A2 B2

Any suggestions?

Thanks J

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MCMPP was developed with large-scale dial-in service in mind. It could have worked also in your case if one side would be implemented with only single router, while two routers used on the other side. With pair of routers at each side, It looks like it won't work. On the other hand, even if it'd have worked, then at least half of packets will almost always take sub-optimal path as they'd have to come to SGBP master for processing, meaning one link more for half of the packets. Have you considered using routing solution instead?

Kind regards, iLya

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Charlie Root


Many thanks for the reply. We have considered a simple routing solution. That's basically what we're doing right now. I've disabled the backup path due to a flaky radio though which is causing OSPF to flap over to the other radio link.

I haven't used the multi-chassis MPPP so I wasn't up on the origins of it. I've used MPPP at a number of clients. I prefer it over IMA for sites with 3 or fewer circuits to bond. The ~12% overhead of ATM usually cuts into the budget of most sites.

The way I see it we could use 2 pairs of routers (we have spares collecting dust), each pair with a single T1 between the POPs to provide the physical redundancy we desire and let OSPF provide the fail-over between them and ultimately the wireless backup links. This will work until the bandwidth needs grow to about 80% of the single T1. At that time we'll have to bond them together on a single router and fail-over to the wireless links. I'm hoping that we'll have fiber in the ground between the POPs before that happens though. The other options is to just bond them together now.

Thanks for the info. J

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