Cisco Nexus 3000 series - Disabling a Fast External Failover; Limiting the AS-Path Attribute; Configuring as Confederations

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Cisco Nexus 3000 Series NX-OS Unicast Routing Configuration Guide, NX-OS Release5.0(3)U1(1)
Chapter 6 Configuring Advanced BGP
Configuring Advanced BGP
Disabling a Fast External Failover
Typically, when a BGP router loses connectivity to a directly connected eBGP peer, BGP triggers a fast
external failover by resetting the eBGP session to the peer. You can disable this fast external failover to
limit the instability caused by link flaps.
To disable fast external failover, use the following command in router configuration mode:
Limiting the AS-path Attribute
You can configure eBGP to discard routes that have a high number of AS numbers in the AS-path
attribute.
To discard routes that have a high number of AS numbers in the AS-path attribute, use the following
command in router configuration mode:
Configuring AS Confederations
To configure an AS confederation, you must specify a confederation identifier. To the outside world, the
group of autonomous systems within the AS confederation look like a single autonomous system with
the confederation identifier as the autonomous system number.
To configure a BGP confederation identifier, use the following command in router configuration mode:
To configure the autonomous systems that belong to the AS confederation, use the following command
in router configuration mode:
Command Purpose
no fast-external-failover
Example:
switch(config-router)# no
fast-external-failover
Disables a fast external failover for eBGP peers.
This command is enabled by default.
Command Purpose
maxas-limit number
Example:
switch(config-router)# maxas-limit 50
Discards eBGP routes that have a number of
AS-path segments that exceed the specified limit.
The range is from 1 to 2000.
Command Purpose
confederation identifier as-number
Example:
switch(config-router)# confederation
identifier 4000
Configures a confederation identifier for an AS
confederation. This command triggers an
automatic notification and session reset for the
BGP neighbor sessions.