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New Member

Load Sharing between two ISP's

We have two via one ISP, let it be ‘A’ and another via another ISP, let it be ‘B’, whose gateway is ISP ‘A’. Now what happens is that it is taking only one path, i.e, the path which is directly connected to ISP ‘A’. This is because AS-path is more when we go via ISP ‘B’. So now I want a solution so that I can load balance via ISP ‘A’ and ISP ‘B’.

New Member

Re: Load Sharing between two ISP's

You have not specified the protocols u use to connect to these ISP's.As you have mentioned the matrix factor of AS number I assume u run BGP with them.As far as my experience it is hard to load balance with two different AS's as we do with the same AS. You can better go for some policy routing where you can share your networks between the two ISP's and reduce the imbalance.



New Member

Re: Load Sharing between two ISP's

Yep..The routing protocol is BGP and again, Also we don't want to subnet the existing pool.

New Member

Re: Load Sharing between two ISP's

Incoming traffic:

It is very hard to load share incoming traffic in your scenario unless you can modify AS path.

Outgoing traffic:

You could use local preference if you are running IBGP inside your AS. If you are running any IGP protocols then advertise two equal cost default routes inside your AS.



Re: Load Sharing between two ISP's


You have to modify total advertising routes policies through route-maps and prefix-lists. And one more thing, please try to give adequate information to help further like your networks size, how you want to advertise those networks, bandwidths of your both ISP's to you etc.



With best regards... Ashok ----------- Pls kindly rate if helpful or answered your question.
New Member

Re: Load Sharing between two ISP's


From your post I gather that you own your own AS, and your IP pool it tie to it. If your network support only a single /24 subnet, then forget about balancing incomming traffic, since Tier1 ISP's will not accept anything higher then a /24. If you have multiple /24's, you can use AS-Path prepend which allows you to annonce your subnets with added AS numbers when annoucing them to your upstream ISP. The ISP that received the subnet with the extra AS numbers will become the backup.

Good Luck

Don Lakey

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