Dell S4048T, Configuration Manual

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Enabling BGP
By default, BGP is not enabled on the system. Dell Networking OS supports one autonomous system (AS) and
assigns the AS number (ASN).
To establish BGP sessions and route traffic, configure at least one BGP neighbor or peer.
In BGP, routers with an established TCP connection are called neighbors or peers. After a connection is
established, the neighbors exchange full BGP routing tables with incremental updates afterward. In addition,
neighbors exchange KEEPALIVE messages to maintain the connection.
In BGP, neighbor routers or peers can be classified as internal or external. External BGP peers must be
connected physically to one another (unless you enable the EBGP multihop feature), while internal BGP peers
do not need to be directly connected. The IP address of an EBGP neighbor is usually the IP address of the
interface directly connected to the router. First, the BGP process determines if all internal BGP peers are
reachable, then it determines which peers outside the AS are reachable.
NOTE: Sample Configurations for enabling BGP routers are found at the end of this chapter.
1 Assign an AS number and enter ROUTER BGP mode.
CONFIGURATION mode
router bgp as-number
•
as-number
: from 0 to 65535 (2 Byte) or from 1 to 4294967295 (4 Byte) or 0.1 to 65535.65535
(Dotted format).
Only one AS is supported per system.
NOTE: If you enter a 4-Byte AS number, 4-Byte AS support is enabled automatically.
a Enable 4-Byte support for the BGP process.
NOTE: This command is OPTIONAL. Enable if you want to use 4-Byte AS numbers or if
you support AS4 number representation.
CONFIG-ROUTER-BGP mode
bgp four-octet-as-support
NOTE: Use it only if you support 4-Byte AS numbers or if you support AS4 number
representation. If you are supporting 4-Byte ASNs, enable this command.
Disable 4-Byte support and return to the default 2-Byte format by using the
no bgp four-
octet-as-support
command. You cannot disable 4-Byte support if you currently have a 4-Byte
ASN configured.
Disabling 4-Byte AS numbers also disables ASDOT and ASDOT+ number representation. All AS
numbers are displayed in ASPLAIN format.
b Enable IPv4 multicast or IPv6 mode.
CONFIG-ROUTER-BGP mode
Border Gateway Protocol IPv4 (BGPv4) 227