3com S7906E 설치 설명서

 

1-9 

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Select the route with the smallest next hop cost 

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Select the route with the shortest CLUSTER_LIST 

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Select the route with the smallest ORIGINATOR_ID 

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Select the route advertised by the router with the smallest Router ID 

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Select the route with the lowest IP address 

 

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CLUSTER_IDs of route reflectors form a CLUSTER_LIST. If a route reflector receives a route that 

contains its own CLUSTER ID in the CLUSTER_LIST, the router discards the route to avoid routing 

loops.  

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If load balancing is configured, the system selects available routes to implement load balancing. 

 

The next hop of a BGP route may not be directly connected. One of the reasons is next hops in routing 

information exchanged between iBGPs are not modified. In this case, the BGP router needs to find the 

directly connected next hop via IGP. The matching route with the direct next hop is called the recursive 

route. The process of finding a recursive route is route recursion. 

Currently, the system supports BGP load balancing based on route recursion, namely, if multiple 

recursive routes to the same destination are load balanced (suppose three direct next hop addresses), 

BGP generates the same number of next hops to forward packets. Note that BGP load balancing based 

on route recursion is always enabled by the system rather than configured using commands.  

BGP differs from IGP in the implementation of load balancing in the following: 

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IGP routing protocols such as RIP, OSPF compute metrics of routes, and then implement load 

balancing over routes with the same metric and to the same destination. The route selection 

criterion is metric. 

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BGP has no route computation algorithm, so it cannot implement load balancing according to 

metrics of routes. However, BGP has abundant route selection rules, through which, it selects 

available routes for load balancing and adds load balancing to route selection rules.