BGP Routing principle:
1, Prefer highestWeight(Local to Router).
The preferred weighted route < weight is a Cisco proprietary property that is used only for the current router >
2, Prefer highestLocal Preference(Global within as).
Highest local priority routing < local priority for as internal >
3. Prefer Routeoriginated by the local routeR (Next hop = 0.0.0.0).
The current router advertises the route <BGP table, and the next hop of the current router-generated route is 0.0.0.0>
4, Prefer ShortestAs path.
Shortest route as Path
5, Prefer lowestOriginCode (IGP < EGP < incomplete).
Compare Origin attribute <IGP precedence over EGP priority incomplete>
6, Prefer lowestMED(exchanged between autonomous systems).
Med min < default does not compare Med values from different as routes and can compare med> of different as with BGP always-compare-med
7, PreferEBGPPath over IBGP path.
External path (EBGP) takes precedence over internal path (IBGP)
8. Prefer the path through theclosest IGP neighbor
Select the path through the nearest IGP neighbor < This means that the router prefers the shortest internal path in the as-the shortest path to BGP next hop)--IBGP
9, balance traffic
If you have configuredMaximum-path,Multiple routes are installed to the routing table < But BGP continues to be more than just one hit >
10, PreferOldest routeFor EBGP paths.
is the external path, select the first received (oldest) < purpose is to reduce jitter >
11. Prefer the path with the lowest neighbor BGPRouter ID.
Preferred route for BGP routers from the lowest route ID
12, Prefer ShortestCluster list
Path with the lowest cluster list length
13. Prefer the path with the lowest neighborIP Address.
The path of the lowest neighbor address.
BGP Load Balancing: Maximum-path (2-16)
Http://wenku.baidu.com/link?url=widt_IQmt60JMfPpCoZ44aPLvV4kT3_ Ous17bl50d1aexllmrbt8fdpyac3kfayat9plzr12hlrlhptkfzl6yu-ktj-ib4bjscrjjdifdki
O (∩_∩) o~