ISP connection with 3 WAN serial links

Unanswered Question
Apr 23rd, 2009
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Hi pro,

Due to the establishment of a new Internet connection via our ISP, we have 3*2 Mbps Wan serial links.

My questions :

- Is it correct to declare 3 default gateways on my edge router ?

- How to make these three (3) Wan links works as a single link with the total bandwidth ?

- How to configure load balance between Wan links ?

- How to configure NAT over the three links ?

Best Regards,


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Overall Rating: 3 (2 ratings)
Giuseppe Larosa Thu, 04/23/2009 - 01:44
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Hello Mustapha,

if your provider cooperates you can use PPP multilink to bundle the three links.

in that case the ip address is associated only to the multilink logical interface and you need only one default gateway.

the multilink logical interface becomes also the NAT outside interface

I think bundling is to be preferred for handling the NAT issue

PPP multilink has its own per packet load balancing algorythm.

For PPP multilink see

Hope to help


Sureshdank Thu, 04/23/2009 - 02:00
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You also configure the load balancing on three links by enabling ip cef and give default routes towards three Serial Interfaces. You also need to ask your ISP to route the Public IP segment towards all the three WAN links so that when load balancing can be achieved completely.

Please rate if helpfull.


Suresh Kumar


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