Bonding/MLPPP with different size Circuits

Unanswered Question
Oct 22nd, 2007

I have a customer with a point to point T1 that has a drop and insert DSU to a PBX (16 data, 8 voice). They want to install a second T1 but want to bond these 24 channels with the 16 channels on the other one, to make it appear as if it is one circuit. I know that MLPPP is simple with two standard T1 circuits, but not sure about circuits with different number of channels. I heard that new code on an ISR is capable of doing this, but has anyone tested this?

My thought is to use a drop and insert module for the 1st circuit and a VWIC for the second router.

I have this problem too.
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Paolo Bevilacqua Mon, 10/22/2007 - 08:40

Hi,

the difference in speed is likely to give you problems anyway.

Better would be a simple load sharing and no MLPPP.

As alternative you can carry the 8 voice channels over IP, and bond the T1 as you like.

derrickhimes Mon, 10/22/2007 - 08:43

from a load sharing perspective, does each circuit (T1) have its own IP address for the gateway? I dont want to have multiple addresses, as this will force me to use each t1 for different types of traffic.

royalblues Mon, 10/22/2007 - 08:42

I dont think you can map 24 channels on one side to 16 channels on the other on a single circuit

You can certainly do multilink between different bandwidth links (one link being a T1 and the other a fractional) but i have seen some absurd results on the same.

Have a look at this link

http://forums.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Network%20Infrastructure&topic=WAN%2C%20Routing%20and%20Switching&CommCmd=MB%3Fcmd%3Dpass_through%26location%3Doutline%40%5E1%40%40.1ddc720b/18#selected_message

HTH

Narayan

guruprasadr Mon, 10/22/2007 - 21:54

HI Narayan,

Well and Wish to hear same from you.

Hope You are Busy all these days.

I was really wondering on seeing the details on Link provided by You reg : Multilink Loadbalancing.

Thanks for INFO and have rated your POST.

Best Regards,

Guru Prasad R

jerry.bonner Mon, 10/22/2007 - 14:23

You can do that. And yeah, either a D & I MFT card to give those 8 voice to the pbx, or perhaps their DSU can just give you a t1 with 16 channels of data. Then just configuration a fractional t1 (timeslots 1-16). Pay attention to your clocking though.

MLPPP will do unequal cost balancing and typically get the bandwidth right on new IOS's with minimal config.

This is from my experience with 2600/2800 etc.

hope that helps.

Paolo Bevilacqua Mon, 10/22/2007 - 15:02

Even in light of experience I should agree with Jerry. MLPPP always sends in the the less congested interface, and the delay difference isn't to large to cause problems in reassembly. Would definitely give MLPPP a shot.

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