Load Balancing between multiple BGP peer connections

Tom Sands tsands at rackspace.com
Wed Sep 14 18:27:27 UTC 2005


Is the connectivity with 1 provider or 3 separate provider?  The diagram 
and wording would seem like its the same.



Patrick W. Gilmore wrote:

>
> [Wow, operational content - thank you!]
>
> On Sep 14, 2005, at 6:24 AM, Joe Shen wrote:
>
>>
>> How could load on multiple BGP peer links be balanced
>> automatically?
>>
>> The situation we are facing:
>>
>>              ---------------------------|
>>              |  Service provider        |
>>              |                          |
>>              --R1--------------------R2---
>>                |\                     |
>>                | \       E-BGP        |
>>                |  \ ----------------\ |
>>                |                     \|
>>             ----R3--------------------R4-|
>>             |     Our Network            |
>>             |      (OSPF)                |
>>             -----------------------------
>>
>> The three links between our network and Service
>> provider network are all 1Gbps. Now, we noticed that
>> load on link R1-R3, R1-R4 is about 50% (in/out), but
>> load on R2-R4 are about 90% ( in/out).
>>
>> How could we balance those load on the three links
>> automatically? or must we tune the route mannually?
>
>
> It's not really clear whether the traffic is going mostly in or  
> mostly out.  In fact, it looks like you are 1:1 balanced from the  
> paragraphs above.
>
> Inbound traffic and outbound traffic need to be balanced separately.   
> I'll do inbound here, since that's slightly harder.  If you need help  
> with outbound too, let us know.
>
>
> First, what are you announcing to your SP?  Is it just one big  
> block?  Or several?
>
> Second, does your SP accept MEDs?  (And if not, maybe you need a new  
> one? :-)
>
> If you have just one big block, split it up into multiple little  
> blocks.  Announce them with MEDs or prepend on some links and not  
> others or just announce a subset on each link.  Be sure to set  
> NO_EXPORT on the little blocks, and announce the aggregate prefix on  
> all links.  You do not want the little blocks making it into the  
> global table (wouldn't do any good anyway).
>
> It's not difficult to do, it's just a bit of trial-and-error to get  
> right unless you have Flow Stats or something so you know where the  
> traffic is going anyway.
>
>
> Outbound is a variation on this theme.  Let us know if you need  
> outbound help as well.
>
> Good luck.
>

-- 
------------------------------------------------------
Tom Sands			  				
Chief Network Engineer				
Rackspace Managed Hosting	    	       
(210)447-4065		   	
------------------------------------------------------





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