Settlements For Problems In Large-Scale Bgp Networks - HP FlexFabric 12900E Series Configuration Manual

Figure 54 Network diagram
Router A
AS 200
Router B

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
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
Route flapping (a route comes up and disappears in the routing table frequently) causes BGP to
send many routing updates. It can consume too many resources and affect other operations.
In most cases, BGP runs in complex networks where route changes are more frequent. To
solve the problem caused by route flapping, you can use BGP route dampening to suppress
unstable routes.
BGP route dampening uses a penalty value to judge the stability of a route. The bigger the
value, the less stable the route. Each time a route state changes from reachable to unreachable,
or a reachable route's attribute changes, BGP adds a penalty value of 1000 to the route. When
the penalty value of the route exceeds the suppress value, the route is suppressed and cannot
become the optimal route. When the penalty value reaches the upper limit, no penalty value is
added.
If the suppressed route does not flap, its penalty value gradually decreases to half of the
suppress value after a period of time. This period is called "Half-life." When the value decreases
to the reusable threshold value, the route is usable again.
Router D
Router C
AS 100
Router E
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