Brocade Multi-Service IronWare Routing Configuration Guide (Supporting R05.6.00) - Manual (Page 58)

30 Multi-Service IronWare Routing Configuration Guide
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Four-byte Autonomous System Numbers (AS4)
Normally, AS4s are sent only to a device, peer group, or neighbor that is similarly configured for
AS4s. If a AS4 is configured for a local-AS, the system signals this configuration by sending
AS_TRANS in the My Autonomous System field of the OPEN message. However, if the AS4 capability
for a neighbor is disabled, the local device does not send the four-octet Autonomous System
number capability to the neighbor.
Enabling AS4 numbers
This section describes how to enable the announcement and negotiation of AS4s and describes
the different types of notation that you can use to represent a AS4.
You can enable AS4s on a device, a peer group, and a neighbor. For global configuration, the
capability command in the BGP4 configuration context enables or disables AS4 support. For a peer
group or a neighbor, capability is a keyword for the neighbor command. In addition to enabling
AS4s for a neighbor or a peer group, you can also use the combination of the capability keyword
and the optional enable or disable keyword to disable this feature in a specific case where the
AS4s are enabled for a larger context. The
“Neighbor configuration of AS4s” section illustrates this
capability.
Global AS4 configuration
To enable AS4s globally, use the capability command in the BGP4 configuration context, as shown.
Brocade(config-bgp)# capability as4 enable
Syntax: [no] capability as4 enable | disable
The no form of the capability command deletes the announcement and negotiation configuration
of AS4s (if it has been enabled) at the global level. Using the regular form of the command with the
disable keyword has the same effect on the global configuration. Disabling or using the no form of
the command does not affect the configuration at the level of a peer or neighbor.
The consequences of choosing between the enable or disable keyword are reflected in the output
of the show running configuration command.
Peer group configuration of AS4s
To enable AS4s for a peer group, use the capability keyword with the neighbor command in the
BGP4 configuration context, as the following example for the Peergroup_1 peer group illustrates.
Brocade(config-bgp)# neighbor Peergroup_1 capability as4 enable
Syntax: [no] neighbor peer-group-name capability as4 enable | disable
The no form of the neighbor command along with the capability as4 keywords disables the
announcement and negotiation of AS4s in the named peer group. Using the regular form of the
command with the disable keyword has the same effect on the neighbor configuration.
The consequences using the enable or disable keywords are reflected in the output of the show
running configuration command. However, if the peer group configuration omits an explicit AS4
argument, the show running configuration output will not contain AS4 information.
Neighbor configuration of AS4s
To enable AS4s for a neighbor, use the capability and as4 keywords with the neighbor command in
the BGP4 configuration context, as the following example for IP address 10.1.1.1 illustrates.
Brocade(config-bgp)# neighbor 10.1.1.1 capability as4 enable
Syntax: [no] neighbor IP address capability as4 enable | disable