Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.14.1.0 - Page 193

Enabling BGP By default, BGP is disabled on the system. Dell EMC Networking OS supports one autonomous system (AS) and assigns the AS number (ASN). To enable the BGP process and begin exchanging information, assign an AS number and use commands in ROUTER BGP mode to configure a BGP neighbor. 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. Following is the sample configuration steps to enable BGP, configure a BGP router-id and network for a router. The same configurations have to be repeated with appropriate changes in the IP addresses for a peer or router to achieve BGP session between two devices. In the below configuration example, no address family is configured. So, the routing information for the IPv4 unicast address family is advertised by default. 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. 2 Enable 4-Byte support for the BGP process. CONFIG-ROUTER-BGP mode bgp four-octet-as-support NOTE: This command is OPTIONAL. Use it only if you support 4-Byte AS numbers or if you support AS4 number representation. Disable 4-Byte support and return to the default 2-Byte format by using the no bgp four-octet-assupport command. You cannot disable 4-Byte support if you currently have a 4-Byte ASN configured. 3 Add a neighbor as a remote AS. CONFIG-ROUTER-BGP mode neighbor {ip-address | peer-group name} remote-as as-number • ip-address: IP address of the neighbor • peer-group name: 16 characters • as-number: from 0 to 65535 (2 Byte) or from 1 to 4294967295 (4 Byte) or 0.1 to 65535.65535 (Dotted format) NOTE: Neighbors that are defined using the neighbor remote-as command in the CONFIGURATION-ROUTER-BGP mode exchange IPv4 unicast address prefixes only. To exchange other address prefixes (IPv6/IPv4 multicast), the neighbors must be activated using neighbor activate command under the respective address family configuration such as address-family ipv6 unicast (for IPv6) and address-family ipv4 multicast (for IPv4 multicast). You must Configure Peer Groups before assigning it a remote AS. Border Gateway Protocol version 4 (BGPv4) 193