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Thread Index Re:[isp-bgp] load balancing with EBGP
Hello. Outbound load balancing to two different providers is absolutely possible! The simplest way is to accept only a default route from each provider, and leave ip route-cache turned on on the interfaces connected to the ISP. In this scenario, the trafffic will not be "truly" load balanced, because traffic to one destination will always take only one link because of he route-cache. This is called "per-destination load balancing" and it works really well. The second option, which is slightly more complicated to configure, allows you to still use the best path abilities of BGP and still quasi-load balance. To do this, you accept a full routing table from both providers, and then use route-maps to modify the routes recieved from each provider to make the routes recieved roughly equal in as-path length. This sounds really complicated, but in practice it's not too bad. Example 1. ISP1 MCI --- EXAMPLENETWORK -- ISP2 ATT In this scenario, you have two isps of roughly the same size. Simply accepting a full routing table from both providers would probably result in decent load balancing. It will never be exactly 50/50, but should be ok. Example 2. ISP1 MCI --- EXAMPLENETWORK -- ISP2 Mom&PopIsp For this situation, you have a big isp, and a small ISP. To load balance here will require you to as-prepend the routes from MCI as you recieve them, to make the smaller ISP's routes look better to your router. All of this has been related to outbound (from you to the internet) traffic. It is also possible to roughly load-balance your traffic inbound from the internet. The quick version of this is you use as-prepends, and in some cases provider defined communities to make the internet see both of the routes you advertise as roughly equal. Other thoughts. Sockeye, which has been bought by Internap, and they are selling it under a different name makes a box that will dynamically adjust bgp and do load balancing outbound. We demo'd one, and it works. Personally, I felt it was too expensive, but internap may have dropped the pricing. Two default routes should not tax the memory of even the lowest cisco router. A full routing table from two providers will barely squeeze into 128mb, and you should look for a router with 256mb if you don't want to upgrade in a year. <plug> I offer BGP and Network consulting services. If you are interested in outsourcing this to someone with years of ISP and enterprise experience, please keep me in mind. </plug> Ejay Hire Network Engineer CCNP/CCDP _________________________________________________________________On Sun, 21 Nov 2004 21:15:05 -0800 (PST), suraj <suraj_rt@...> wrote: > Hi, >=20 > Please provide me the solution to the following > problem; >=20 > Protocol running :BGP > Scenario: We have a single router where two different > links of that router are terminated with two differnt > service providers.These links are used for internet to > ours users sitting in our Lan.Is it possible to make > utilize these two links simultaniously( Is it posible > to load balance these two links using the BGP,I > believe Load balancing is not possible with BGP as BGP > takes the best path).PLease let me know whether is > there any other way to acheive load sharing/load > balancing with BGP? >=20 > Suraj > Consultant > ACC technologies Express yourself instantly with MSN Messenger! Download today - it's FREE! http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/ To unsubscribe via postal mail, please contact us at: Jupitermedia Corp. Attn: Discussion List Management 475 Park Avenue South New York, NY 10016 Please include the email address which you have been contacted with.
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