Huawei S6700 Series Configuration Manual page 447

S6700 Series Ethernet Switches
Configuration Guide - IP Routing
complex networks where routes change frequently. Frequent route flapping consumes lots of
bandwidth and CPU resources and even seriously affects network operations.
BGP route dampening prevents frequent route flapping by using a penalty value to measure route
stability. When a route flaps for the first time, a penalty value is assigned to the route. Later,
each time the route flaps, the penalty value of the route increases by a specific value. The greater
the penalty value, the less stable the route. If the penalty value of a route exceeds the pre-defined
threshold, the route will not be advertised until the penalty value of the route reduces to the reuse
threshold.
Route dampening applies only to EBGP routes. IBGP routes, however, cannot be dampened.
Generally, IBGP routes include routes from the local AS, requiring that the forwarding tables
be the same. In addition, IGP fast convergence aims to achieve information synchronization. If
IBGP routes are dampened, dampening parameters vary on different devices, and the forwarding
tables are inconsistent.
Pre-configuration Tasks
Before configuring BGP route dampening, complete the following task:
l
Procedure
Step 1 Run:
system-view
The system view is displayed.
Step 2 Run:
bgp as-number
The BGP view is displayed.
Step 3 Run:
ipv4-family unicast
The IPv4 unicast address family view is displayed.
Step 4 Run:
dampening [ half-life-reach reuse suppress ceiling | route-policy route-policy-
name ]
BGP route dampening parameters are set.
When you configure BGP route dampening, the values of reuse, suppress, and ceiling should
meet the relationship of reuse<suppress<ceiling.
If routes are differentiated based on policies and the dampening command is run to reference
a route-policy, BGP can use different route dampening parameters to suppress different routes.
----End
Issue 01 (2012-03-15)
Configuring Basic BGP Functions
*
NOTE
The dampening command takes effect only for EBGP routes.
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