Concept Guide

router bgp 100
bgp four-octet-as-support
neighbor 172.30.1.250 local-as 65057
<output truncated>
DellEMC(conf-router_bgp)#do sho ip bgp
BGP table version is 28093,
local router ID is 172.30.1.57
AS4 SUPPORT DISABLED
DellEMC(conf-router_bgp)#no bgp four-octet-as-support
DellEMC(conf-router_bgp)#sho conf
!
router bgp 100
neighbor 172.30.1.250
local-as 65057
DellEMC(conf-router_bgp)#do show ip bgp
BGP table version is 28093, local router ID is 172.30.1.57
Four-Byte AS Numbers
You can use the 4-Byte (32-bit) format when conguring 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 dierent 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 identied routers. You cannot mix them.
Congure 4-byte AS numbers with the bgp four-octet-as-support command.
BGP router ID
A router ID is used to identify neighbors congured with BGP. The BGP router ID is a user given ID to a BGP router, which is unique 32-bit
value IPv4 address. The router ID is the highest IP address of the Loopback interface and if no Loopback interfaces are congured, Dell
EMC Networking OS selects the highest IP address of a physical interface on the router as the router ID.
Sessions and Peers
When two routers communicate using the BGP protocol, a BGP session is started. The two end-points of that session are called neighbors
or peers. A local device does not identify a BGP peer automatically. You have to manually congure the connections between BGP running
devices. BGP uses TCP connection to communicate with another BGP neighbor. After establishing a TCP connection between the peers,
each peer exchange route information with other peer.
Border Gateway Protocol (BGP)
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