Users Guide

Command Settings BGP Local Routing
Information Base
MED Advertised to Peer
WITH route-map metric-type
internal
MED Advertised to Peer
WITHOUT route-map
metric-type internal
redistribute isis metric 100 MED: IGP cost 100 MED: 100 MED: 100
Ignore Router-ID in Best-Path Calculation
You can avoid unnecessary BGP best-path transitions between external paths under certain conditions. The bgp bestpath
router-id ignore command reduces network disruption caused by routing and forwarding plane changes and allows for
faster convergence.
Four-Byte AS Numbers
You can use the 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 will be 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, 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 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.
Border Gateway Protocol IPv4 (BGPv4) 169