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Multilink PPP Vs Load Balancing

Hi all,

I have previously posed a question about 'combining' 2 PVCs bandwidth into a single one.

I have been given the solution of Multilink PPP over ATM and over FR.

However, i found out that i can do load balancing (automatically done by the router), even with static routes, as long as there are 2 or more path to the same desination subnet ...

So my question is this,

Why should i go in to the trouble of configuring Multilink PPP and not the simple load balancing method ???

What are the advantages and disadvantages of each one and how would u compare them ???

I hope u can solve this for me,

Thanks,

George

1 ACCEPTED SOLUTION

Accepted Solutions
Purple

Re: Multilink PPP Vs Load Balancing

Hi George,

There is one very important difference between using one large "virtual interface" compared to multiple lower bandwidth interfaces.

It has to do with the way switching mechanisms like CEF and Fast switching perform load-balancing. When you have multiple equal cost routes going over different interfaces, CEF/Fast switching will automatically load balance over them. However, since the load balancing will be performed per-destination by default (although per-packet is an option with CEF), the maximum bandwidth any flow can get is limited to the size of a single link. When using multilink interfaces, the maximum bandwidth a flow can get is now the aggregate bandwidth of all the physical interfaces in the bundle.

For example, if you have 2 E1 interfaces, the max bandwidth a flow can get is an E1 rate. If you use multilink PPP and bundle these 2 E1s, a single flow can now get 2xE1 worth of traffic.

Hope that helps - pls rate the post if it does.

Regards,

Paresh.

1 REPLY
Purple

Re: Multilink PPP Vs Load Balancing

Hi George,

There is one very important difference between using one large "virtual interface" compared to multiple lower bandwidth interfaces.

It has to do with the way switching mechanisms like CEF and Fast switching perform load-balancing. When you have multiple equal cost routes going over different interfaces, CEF/Fast switching will automatically load balance over them. However, since the load balancing will be performed per-destination by default (although per-packet is an option with CEF), the maximum bandwidth any flow can get is limited to the size of a single link. When using multilink interfaces, the maximum bandwidth a flow can get is now the aggregate bandwidth of all the physical interfaces in the bundle.

For example, if you have 2 E1 interfaces, the max bandwidth a flow can get is an E1 rate. If you use multilink PPP and bundle these 2 E1s, a single flow can now get 2xE1 worth of traffic.

Hope that helps - pls rate the post if it does.

Regards,

Paresh.

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