Users Guide

Table 11. Redistributed Route Rules
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 (IGP cost
= 20)
MED: IGP cost 20 MED = 20 MED = 0
redistribute isis route-
map set metric 50
MED: IGP cost 50 MED: 50 MED: 50 MED: 50 MED: 50
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.
Border Gateway Protocol IPv4 (BGPv4) 215