Settlements For Problems In Large-Scale Bgp Networks - HPE FlexNetwork HSR6800 Configuration Manual

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 63 Network diagram
In Figure 63, 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
Route summarization can reduce the BGP routing table size by advertising summary routes
rather than more specific routes.
The system supports both manual and automatic route summarization. Manual route
summarization allows you to determine the attribute of a summary route and whether to
advertise more specific routes.
•
Route dampening
BGP route dampening solves the issue of route instability such as route flaps—a route comes
up and disappears in the routing table frequently.
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"BGP route