188 | Border Gateway Protocolw w w . d e l l . c o m | s u p p o r t . d e l l . c o m 4-Byte AS NumbersFTOS Version 7.7.1 and later support 4-Byte (32-bit) format when configuring Autonomous SystemNumbers (ASNs). The 4-Byte support is advertised as a new BGP capability (4-BYTE-AS) in the OPENmessage. If a 4-Byte BGP speaker has sent and received this capability from another speaker, all themessages will be 4-octet. The behavior of a 4-Byte BGP speaker will be different with the peer dependingon whether the peer is 4-Byte or 2-Byte BGP speaker.Where the 2-Byte format is 1-65535, the 4-Byte format is 1-4294967295. Enter AS Numbers using thetraditional format. If the ASN is greater than 65535, the dot format is shown when using the show ip bgpcommands. For example, an ASN entered as 3183856184 will appear in the show commands as48581.51768; an ASN of 65123 is shown as 65123. To calculate the comparable dot format for an ASNfrom a traditional format, use ASN/65536. ASN%65536.When creating Confederations, all the routers in a Confederation must be either 4-Byte or 2-Byte identifiedrouters. You cannot mix them.Configure the 4-byte AS numbers with the four-octet-support command.AS4 Number RepresentationFTOS version 8.2.1.0 supports multiple representations of an 4-byte AS Numbers: asplain, asdot+, andasdot.ASPLAIN is the method FTOS has used for all previous FTOS versions.It remains the default method withFTOS 8.2.1.0 and later. With the ASPLAIN notation, a 32 bit binary AS number is translated into adecimal value.• All AS Numbers between 0-65535 are represented as a decimal number when entered in the CLI aswell as when displayed in the show command outputs.• AS Numbers larger than 65535 are represented using ASPLAIN notation as well. 65546 isrepresented as 65546.Table 9-2. 4-Byte ASN Dot Format ExamplesTraditional Format Dot Format65001 Is 0.6550165536 The 1.0100000 Same As 1.344644294967295 65535.65535Note: The ASDOT and ASDOT+ representations are supported only in conjunction with the 4-Byte ASNumbers feature. If 4-Byte AS Numbers are not implemented, only ASPLAIN representation is supported.
