F3215-HP Load Balancing Module Appendix Protocol Reference-6PW101

the same number of next hops to forward packets. BGP load balancing based on route recursion

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

• BGP load balancing through route selection

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

{ IGP routing protocols, such as RIP and 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.

{ 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.

BGP implements load balancing only on routes that have the same AS_PATH, ORIGIN,

LOCAL_PREF and MED, rather than using the route selection rules as described in "BGP route

sel

ect

ion."

Figure 14 Network diagram

In Figure 14, Router A and Router B are IBGP peers of Router C. Router D and Router E both advertise a

route 9.0.0.0 to Router C. If load balancing with a maximum number of two routes is configured on

Router C, and the two routes have the same AS_PATH, ORIGIN, LOCAL_PREF, and MED, Router C

installs both the two routes to its routing table for load balancing. After that, Router C forwards to Router

A and Router B a single route that has NEXT_HOP changed to Router C without changing other

attributes.

NOTE:

BGP load balancing is applicable between EBGP peers, between IBGP peers, and between

confederations.

Settlements for problems in large-scale BGP

networks

For easy management and route distribution efficiency, use the following methods on a large-scale BGP

network:

• Route summarization