Bgp Route Selection; Stripping Out Private As Numbers From Route Updates - Extreme Networks ExtremeWare XOS Guide Manual

Viewing the Route Flap Dampening Configuration
To view the configured values of the route flap dampening parameters for a BGP neighbor, use the
following command:
show bgp [neighbor {detail} | neighbor <remoteaddr>]
To view the configured values of the route flap dampening parameters for a BGP peer group, use the
following command:
show bgp peer-group {detail | <peer-group-name> {detail}}
To display the dampened routes, use the following command:
show bgp neighbor <remoteaddr> {address-family [ipv4-unicast | ipv4-multicast]} flap-
statistics {detail} [all | as-path <path-expression> | community [no-advertise | no-
export | no-export-subconfed | number <community_num> | <AS_Num>:<Num> ] | network
[any / <netMaskLen> | <networkPrefixFilter>] {exact} ]

BGP Route Selection

BGP selects routes based on the following precedence (from highest to lowest):
higher weight
●
higher local preference
●
shortest length (shortest AS path)
●
lowest origin code
●
lowest Multi Exit Discriminator (MED)
●
route from external peer
●
lowest cost to next hop
●
lowest routerID
●

Stripping Out Private AS Numbers from Route Updates

Private AS numbers are AS numbers in the range 64512 through 65534. You can remove private AS
numbers from the AS path attribute in updates that are sent to external BGP (EBGP) neighbors. Possible
reasons for using private AS numbers include:
The remote AS does not have officially allocated AS numbers.
●
You want to conserve AS numbers if you are multihomed to the local AS.
●
Private AS numbers should not be advertised on the Internet. Private AS numbers can be used only
locally within an administrative domain. Therefore, when routes are advertised out to the Internet, the
routes can be stripped out from the AS paths of the advertised routes using this feature.
To configure private AS numbers to be removed from updates, use the following command:
enable bgp neighbor [<remoteaddr> | all] remove-private-AS-numbers
To disable this feature, use the following command:
disable bgp neighbor [<remoteaddr> | all] remove-private-AS-numbers
ExtremeWare XOS 11.1 Concepts Guide
BGP Features
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