Administrator Guide

incremented. Use the show ip bgp neighbors command to view the “failed enforce-first-as check”
counter.
If you disable enforce-first-as, you can view it using the show ip protocols command.
Related
Commands
● show ip bgp neighbors – views the information exchanged by BGP neighbors.
● show ip protocols – views information on routing protocols.
bgp fast-external-fallover
Enable the fast external failover feature, which immediately resets the BGP session if a link to a directly connected external peer
fails.
C9000 Series
Syntax
bgp fast-external-fallover
To disable fast external fallover, use the no bgp fast-external-fallover command.
Defaults Enabled.
Command Modes ROUTER BGP
Command
History
Version Description
9.9(0.0) Introduced on the C9010.
9.2(1.0) Introduced on the Z9500.
8.2.1.0 Introduced on the E-Series ExaScale.
7.4.1.0 Introduced
Usage
Information
The bgp fast-external-fallover command appears in the show config command output.
bgp four-octet-as-support
Enable 4-byte support for the BGP process.
C9000 Series
Syntax
bgp four-octet-as-support
To disable fast external fallover, use the no bgp four-octet-as-support command.
Defaults Disabled (supports 2-Byte format).
Command Modes ROUTER BGP
Command
History
Version Description
9.9(0.0) Introduced on the C9010.
9.2(1.0) Introduced on the Z9500.
8.2.1.0 Introduced on the E-Series ExaScale.
7.7.1.0 Introduced
Usage
Information
Routers supporting 4-Byte ASNs advertise that function in the OPEN message. The behavior of a 4-Byte
router is slightly different depending on whether it is speaking to a 2-Byte router or a 4-Byte router.
446 Border Gateway Protocol