Dell Force10 C150 Configuration Manual page 259

Use the following commands in the CONFIGURATION ROUTER BGP mode to configure BGP
confederations.
Command Syntax
bgp confederation identifier
as-number
bgp confederation peers
as-number [... as-number ]
show config
Use the
configuration.
Enable route flap dampening
When EBGP routes become unavailable, they "flap" and the router issues both WITHDRAWN and
UPDATE notices. A flap is when a route
• is withdrawn
• is readvertised after being withdrawn
• has an attribute change
The constant router reaction to the WITHDRAWN and UPDATE notices causes instability in the BGP
process. To minimize this instability, you may configure penalties, a numeric value, for routes that flap.
When that penalty value reaches a configured limit, the route is not advertised, even if the route is up. In
FTOS, that penalty value is 1024. As time passes and the route does not flap, the penalty value decrements
or is decayed. However, if the route flaps again, it is assigned another penalty.
The penalty value is cumulative and penalty is added under following cases:
• Withdraw
• Readvertise
• Attribute change
When dampening is applied to a route, its path is described by one of the following terms:
• history entry—an entry that stores information on a downed route
• dampened path—a path that is no longer advertised
• penalized path—a path that is assigned a penalty
The CLI example below shows configuring values to start reusing or restarting a route, as well as their
default values.
Command Mode
CONFIG-ROUTER-
BGP
CONFIG-ROUTER-
BGP
All Confederation routers must be either 4-Byte or 2-Byte. You cannot have a
mix of router ASN support,
command in the CONFIGURATION ROUTER BGP mode to view the
Purpose
Specifies the confederation ID.
AS-number: 0-65535 (2-Byte) or 1-4294967295
(4-Byte)
Specifies which confederation sub-AS are peers.
AS-number: 0-65535 (2-Byte) or 1-4294967295
(4-Byte)
Border Gateway Protocol IPv4 (BGPv4) | 259