BGP loadbalance incomming traffic.

Unanswered Question
Jun 6th, 2008
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Can someone help me.

I have two providers connected to my one router. I have AS with one public adress space - C class.

How i can loadbalance incomming traffic betwwen this two providers.

Can i split my c class on to two adress spaces with /25 mask and advertise one part on one provider and another part on another provider. ??

Or maybe any better way. ?

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Overall Rating: 3.5 (2 ratings)
blubericisco Fri, 06/06/2008 - 05:10
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Like you said, one way is to split your space in two, BUT.. announce each part to each different providers, with as-path prepending (ie. for a /23 block, announce 1st /24 to first provider, announce 1st /24 to second provider with as-path prepending, then do the inverse for the 2nd /24.)

However, since you have a /24 you can't really split it into two /25s, as they would most likely get filtered by your provider or higher.

So in your case, you would probably need something other than BGP for your incoming load-balancing.

Unless someone else can chime in and enlighten us ;)

hasnain321 Fri, 06/06/2008 - 05:27
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If you want the loadbalancing for incoming traffic then this is the only solution. You need to split the range and advertise it two providers. If that address space is yours not assigned by any service provider then it is easy otherwise you will have to convince one service provider to advertise other service provider address space for you.

-cybermen Fri, 06/06/2008 - 05:42
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And i do not understood part about my adress space being assigned by service prowider. I Have BGP and own AS number and own claass of adreses.

But as blubericisco wrote i cant split /24 network in to two parts with BGP, yes or not ??

blubericisco Fri, 06/06/2008 - 05:56
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What hasnain321 meant, is that your space could have been assigned by a service provider (commonly called PA space), which means that you would need your second ISP to advertise addresses owned by the first ISP.

This is not your case, since you have PI space (provider independent).

As for splitting your /24, it is TECHNICALLY possible, you can split however you want (be that /25,/26, /27 etc). My point was that most service provider will filter announcements higher than /24 (/25 to /32), so while you CAN announce it to your upstream provider, the advertisement would probably never make it in the global routing tables.


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