3Com 7757 Configuration Manual page 360

360 C 36: BGP C
HAPTER ONFIGURATION
Configuring BGP-IGP
Route Synchronization
c
Configuring BGP Route
Dampening
Table 295 Configure BGP route receiving policy
Operation
Filter the Specify an
routing ACL-based
information BGP route
received from filtering
a peer/peer policy for a
group peer/peer
group
Specify an AS
path
ACL-based
BGP route
filtering
policy for a
peer/peer
group
Specify an IP
prefix
list-based
BGP route
filtering
policy for a
peer/peer
group
Table 296 Configure BGP-IGP route synchronization
Operation
Enter system view
Enable BGP, and enter BGP
view
Disable BGP-IGP route
synchronization
CAUTION: BGP-IGP route synchronization is not supported on Switch 7750
Ethernet switches.
Route dampening is used to solve the problem of route instability. Route instability
mainly refers to route flapping. A route flaps if it appears and disappears
repeatedly in the routing table. Route flapping increases the number of BGP
update packets, consumes the bandwidth and CPU time, and even decreases
network performance.
Assessing the stability of a route is based on the behavior of the route in the
previous time. Once a route flaps, it receives a certain penalty value. When the
penalty value reaches the suppression threshold, this route is suppressed. The
penalty value decreases with time. When the penalty value of a suppressed route
decreases to the reuse threshold, the route gets valid and is thus advertised again.
BGP dampening suppresses unstable routing information. Suppressed routes are
neither added to the routing table nor advertised to other BGP peers.
Command
peer { group-name |
ip-address } filter-policy
acl-number import
peer { group-name |
ip-address } as-path-acl
acl-number import
peer { group-name |
ip-address } ip-prefix
ip-prefix-name import
Command
system-view
bgp as-number
undo synchronization
Description
Required
By default, no ACL-based BGP
route filtering policy, AS path
ACL-based BGP route filtering
policy, or IP prefix list-based
BGP route filtering policy is
configured for a peer/peer
group.
Description
-
Required
By default, BGP is disabled.
Required
By default, BGP routes and IGP
routes are not synchronized.