This is one of those posts where the attributions have gotten very confused. Comments inline.
Again, a fundamental question is "what problem are you trying to solve" with the load balancing. If you are getting full routes from multiple well-connected providers, that, in and of itself, should provide a reasonable load split. More importantly, it will pick the best BGP route for every outgoing destination. If you try to "load balance" on top of this, presumably with the goal of optimizing your bandwidth utilization to the ISPs, you are going to have suboptimal end-to-end routing. Is ideal bandwidth utilization on the first hop more important than the end-to-end path? At 11:43 AM -0400 5/27/02, Bob Timmons wrote: > > Chaps.. >> >> can i try to explain something about BGP addressing and you chaps point >out >> were i am or am not going wrong ??.. >> >> EG.. >> >> i have two bgp routers going to the net ... >> >> i am multihomed to 2 service providers...(and accepting FULL routes) >> >> i have been issued 2 "sets" of ip address to my service providers.. >> >> i am using Private AS`s (internally) >> >> >> >> ok .. >> outgoing traffic... >> >> i take it ...as i have full routes then outgoing traffic has no issue`s as >to >> how to get anywhere...(i am using gateway of last resort and a DMZ for all >my >> internal stuff) > >Be sure you're using an IP from each provider 'outbound'. We're doing >something similar >and had to configure the firewall to NAT an IP from each provider or it >won't 'load balance' > >> >> incoming traffic ...routes i advertise out to the net... >> >> if i am multihomed... i have two different ip address`s advertising a >route >> to >> my network ..this would cause no problems as there are simply 2 routes on >the >> net to get to me.. >> >> my service providers will use the same private AS number to get to mee >> ????....( will it matter if they give me two different private as ...as i >> want >> to load balance...).. > >If you're using different ISP's, then I don't believe you can use private >AS's. >(correct me if I'm wrong). It can be done, if both ISPs agree to it and coordinate their routing policies. A public AS, however, is justified in this circumstance. While doesn't quite describe this situation, look at RFC 2270 for the general strategy. Both ISPs have to remove private AS. This will also cause more than one ISP to appear to originate the route, which is a technical violation of BGP (i.e., it's an "inconsistent route"), but that isn't that uncommon and doesn't seem to break anything. >In order to 'load balance' or 'load share' with >BGP >using multiple providers, I believe you'll need a public AS. If you were >only using >one provider, you could get away with a private AS (since the provider is >doing the >BGP advertising for you. > >> >> How would load balancing work.(inbound..) (outbound i understand)... >> ...the >> BGP routers are in the same location ....so it makes no difference >localy.. > >The BGP routers (yours) are in the same location, yes, but the ISP's are >not. The >BGP routes are going through your ISP first, then back to you. Again, I >believe you >need a public AS to advertise through your ISPs to perform any kind of 'load >sharing'. >In this type of scenario, you'll not get true load balancing. You'll need >to tweak your >outgoing traffic to modify your inbound traffic. That said, they are two >disticntly separate >entities (inbound and outbound traffic), so you need to keep that in mind. > >> >> i get the rest it is just this i am bit shakey on...i dont really >understand >> how to different SP can give me load balcning...prehpsa it cant... > >Consider this. You have ISP-A and ISP-B. You also have an IP range from >ISP-A and >ISP-B. When traffic goes out through ISP-A using an IP from ISP-A's range, >it will come >back through ISP-A to get back to you. If you load balance traffic >outbound, it will load >balance inbound (in this scenario). When a host on the Internet 'sees' an >IP from ISP-B >and is responding to it, it will follow the BGP path to ISP-B and therefore >back to you via >ISP-B's pipes. > >> >> many thanks >> >> > > steve Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=45149&t=45149 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
