My internet router are connected to two different ISP.On my server and with both ISP routers, BGP is running. I am using PAT to access the internet. Now I configured two default route on my router, one for each ISP. Now if both ISP's link are connected then one packet is going through onw isp and other packet is going to another ISP. Because of that my internet is very slow. IF I shutdoen any of the one ISP then my internet speed is fine.How can I specify that insted of packet, it will take the datastream for load balance? Please help me to resolve this issue.
First off, enable CEF, that should help a bit.
Second, running BGP should be determining the best route to the destination site, this is not "load-balancing" but it does allow the traffic to take the most efficient route to the destination.
Where this isn't very good is if your using a "Tier-1" ISP for one connection and a "Tier 2 or 3" provider for the second. When this happens, all the "paths" to the destination are more efficient on the Tier-1 link. You can even this out a bit by "padding" the link, ie: artificially making the Tier-1 path longer on both the inbound and outbound traffic.
The basics of BGP are this. BGP figures out the best route by how many AS's are between you and your destination. ie: it doesn't keep track of the # of hops, just the number of AS's it has to cross to get there. So, with a Tier-1 provider the path to most hosts might be an average of 2 AS's it crosses, while on a Tier 2 it might be 3 or 4, while on a Tier 3 it might be 4 or 5. You need to pad the numbers from the Tier 1 to even out the average lengths a bit more.
Check out this message for examples of the outbound, the inbound is the same, but you would need to prepend your neighbors AS # instead...