Settlements For Problems In Large-Scale Bgp Networks - HP 6125XLG Configuration Manual

The system supports BGP load balancing based on route recursion. 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. 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
selection."
Figure 48 Network diagram
In Figure 48, 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 and other attributes changed to
those of the best route.
NOTE:
BGP load balancing is applicable between EBGP peers, between IBGP peers, and between
confederations.

Settlements for problems in large-scale BGP networks

You can use the following methods to facilitate management and improve route distribution efficiency on
a large-scale BGP network.
Route summarization
•
164
"BGP route