Users Guide

This command must be performed on the router which is attaching link bandwidth to prefixes (typically a
border router) as well as the router which is expected to load share traffic proportional to the bandwidth
of the external links.
bgp enforce-first-as
Disable (or enable) enforce-first-as check for updates received from EBGP peers.
Syntax
bgp enforce-first-as
To turn off the default, use the no bgp enforce-first-as command.
Defaults Enabled
Command Modes ROUTER BGP
Command
History
This guide is platform-specific. For command information about other platforms, see the relevant Dell
Networking OS Command Line Reference Guide.
Version Description
9.8(0.0P5) Introduced on the S4048-ON.
9.8(0.0P2) Introduced on the S3048-ON.
9.7(0.0) Introduced on the S6000–ON.
9.0.2.0 Introduced on the S6000.
8.3.19.0 Introduced on the S4820T.
8.3.11.1 Introduced on the Z9000.
8.3.7.0 Introduced on the S4810.
7.8.1.0 Introduced on the S-Series.
7.7.1.0 Introduced on the C-Series.
7.4.1.0 Introduced.
Usage
Information
This command is enabled by default, that is for all updates received from EBGP peers, BGP ensures that
the first AS of the first AS segment is always the AS of the peer. If not, the update is dropped and a
counter is increments. Use the show ip bgp neighbors command to view the “failed enforce-first-
as check” counter.
If you disable the enforce-first-as command, it can be viewed using the show ip protocols
command.
In the event of an enfore-first-as check failure, the existing BGP session is flapped.
Related
Commands
● show ip bgp neighbors — view the information the BGP neighbors exchange.
● show ip protocols — view information on routing protocols.
bgp fast-external-failover
Enable the fast external failover feature, which immediately resets the BGP session if a link to a directly connected external peer
fails.
S5000
Syntax
bgp fast-external-failover
To disable fast external failover, use the no bgp fast-external-failover command.
Border Gateway Protocol 331