Brocade Communications Systems ICX 7250 series, Configuration Manual

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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 1.1.1.1 illustrates.
device(config-bgp)# neighbor 1.1.1.1 capability as4 enable
Syntax: [no] neighbor IPaddress capability as4 enable | disable
The no form of the neighbor command with the capability and as4 keywords deletes the neighbor-enable for AS4s.
The consequences of using the enable or disable keywords are reflected in the output of the show running configuration command.
However, if the neighbor configuration omits an explicit AS4 argument, the show running configuration output will not contain AS4
information.
To disable AS4s on a particular neighbor within a peer group that is enabled for AS4s, enter a command similar to the following.
device(config-bgp)# neighbor 1.1.1.1 capability as4 disable
Specifying the local AS number
The local autonomous system number (ASN) identifies the autonomous system where the BGP4 device resides.
Normally, AS4s are sent only to a device, peer group, or neighbor that is similarly configured for AS4s. Typically, if you try to set up a
connection from an AS4-enabled device to a device that processes only two-byte ASNs, the connection fails to come up unless you
specify the reserved ASN 23456 as the local ASN to send to the far-end device.
To set the local autonomous system number, enter commands such as the following.
device(config)# router bgp
BGP4: Please configure 'local-as' parameter in order to enable BGP4.
device(config-bgp)# local-as 100000
device(config-bgp)# write memory
Syntax: [no] local-as num
The num parameter specifies a local ASN in the range 1 - 4294967295. No default exists for num . ASNs 64512 - 65535 are the
well-known private BGP4 autonomous system numbers and are not advertised to the Internet community.
Route-map set commands and AS4s
You can prepend an AS4 number to an autonomous system path or make the autonomous system number a tag attribute for a route
map as shown here.
device(config-routemap test)# set as-path prepend 7701000
Syntax: [no] set as-path prepend num,num , ... | tag
Use the no form of this command to remove the configuration.
Four-byte Autonomous System Numbers (AS4)
Brocade FastIron Layer 3 Routing Configuration Guide
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