Users Guide

Ignore Router-ID for Some Best-Path
Calculations
Dell Networking OS allows you to avoid unnecessary BGP best-path transitions between external paths under
certain conditions. The bgp bestpath router-id ignore command reduces network disruption routing
causes and forwarding plane changes and allows for faster convergence.
Four-Byte AS Numbers
Dell Networking OS supports 4-Byte (32-bit) format when configuring autonomous system numbers (ASNs).
The 4-Byte support is advertised as a new BGP capability (4-BYTE-AS) in the OPEN message. If a 4-Byte BGP
speaker has sent and received this capability from another speaker, all the messages are 4-octet. The
behavior of a 4-Byte BGP speaker is different with the peer depending on whether the peer is a 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 the
traditional format. If the ASN is greater than 65535, the dot format is shown when using the show ip bgp
commands. For example, an ASN entered as 3183856184 appears in the show commands as 48581.51768; an
ASN of 65123 is shown as 65123. To calculate the comparable dot format for an ASN from a traditional
format, use ASN/65536. ASN%65536.
Traditional
Format
DOT Format
65001 0.65501
65536 1.0
100000 1.34464
4294967295 65535.65535
When creating Confederations (Communities), all the routers in a Confederation must be either 4 Byte or 2
Byte identified routers. You cannot mix them.
Configure 4-byte AS numbers with the four-octet-support command.
AS4 Number Representation
Dell Networking OS supports multiple representations of 4-byte AS numbers: asplain, asdot+, and asdot.
NOTE: The ASDOT and ASDOT+ representations are supported only with the Four-Byte AS Numbers
feature. If 4-Byte AS numbers are not implemented, only ASPLAIN representation is supported.
ASPLAIN is the method Dell Networking OS has used for all previous Dell Networking OS versions. ASPLAIN
remains the default method with Dell Networking OS. With the ASPLAIN notation, a 32-bit binary AS number
is translated into a decimal value.
Border Gateway Protocol IPv4 (BGPv4) 218