Concept Guide
Traditional
Format
DOT Format
65001 0.65501
65536 1.0
100000 1.34464
4294967295 65535.65535
When creating Confederations, all the routers in a Confederation must be either 4-Byte or 2-Byte identied routers. You cannot mix them.
Congure 4-byte AS numbers with the four-octet-support command.
AS4 Number Representation
Multiple representations of 4-byte AS numbers (asplain, asdot+, and asdot) are supported.
NOTE: The ASDOT and ASDOT+ representations are supported only with the 4-Byte AS numbers feature. If 4-Byte AS numbers
are not implemented, only ASPLAIN representation is supported.
ASPLAIN is the default method the system uses. With the ASPLAIN notation, a 32-bit binary AS number is translated into a decimal value.
• All AS numbers between 0 and 65535 are represented as a decimal number when entered in the CLI and when displayed in the show
commands output.
• AS numbers larger than 65535 are represented using ASPLAIN notation. When entered in the CLI and when displayed in the show
commands output, 65546 is represented as 65546.
ASDOT+ representation splits the full binary 4-byte AS number into two words of 16 bits separated by a decimal point (.): <high-order 16 bit
value>.<low-order 16 bit value>. Some examples are shown in the following table.
• All AS numbers between 0 and 65535 are represented as a decimal number, when entered in the CLI and when displayed in the show
commands outputs.
• AS Numbers larger than 65535 is represented using ASDOT notation as <higher 2 bytes in decimal>.<lower 2 bytes in decimal>. For
example: AS 65546 is represented as 1.10.
ASDOT representation combines the ASPLAIN and ASDOT+ representations. AS numbers less than 65536 appear in integer format
(asplain); AS numbers equal to or greater than 65536 appear in the decimal format (asdot+). For example, the AS number 65526 appears
as 65526 and the AS number 65546 appears as 1.10.
Dynamic AS Number Notation Application
A change in the ASN notation type is dynamically applied to the running-cong statements.
When you apply or change an ASN notation, the type selected is reected immediately in the running-conguration and the show
commands (refer to the following two examples).
Example of Dynamic Changes in the Running Conguration When Using the bgp asnotation Command
ASDOT
Dell(conf-router_bgp)#bgp asnotation asdot
Dell(conf-router_bgp)#show conf
!
router bgp 100
bgp asnotation asdot
bgp four-octet-as-support
neighbor 172.30.1.250 local-as 65057
<output truncated>
Dell(conf-router_bgp)#do show ip bgp
BGP table version is 24901, local router ID is 172.30.1.57
<output truncated>
192
Border Gateway Protocol IPv4 (BGPv4)