Dell Configuration Guide for the S4048–ON System 9.14.2.6

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.

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.
Add a BGP neighbor or peer and AS number.
CONFIG-ROUTER-BGP mode

neighbor {ip-address | ipv6-address| peer-group name} remote-as as-number
- ip-address: IPv4 address of the neighbor
- ipv6-address: IPv6 address of the neighbor
- peer-group name: Name of the peer group. It can contain 16 characters.
- as-number: Autonomous number
NOTE Neighbors that are defined using the neighbor remote-as command in the CONFIGURATION-ROUTER-BGP mode exchange IPv4 unicast address prefixes only.
Enable the BGP neighbor.
CONFIG-ROUTER-BGP mode

neighbor {ip-address | ipv6–address | peer-group-name} no shutdown

Example configuration steps to enable BGP

NOTE When you change the configuration of a BGP neighbor, always reset it by entering the clear ip bgp * command in EXEC Privilege mode.

To view the BGP configuration, enter show config in CONFIGURATION ROUTER BGP mode. To view the BGP status, use the show ip bgp summary command in EXEC Privilege mode. The example shows that the summary with a 2-byte AS number using the show ip bgp summary command.

Following is the configuration steps:

DellEMC# configure terminal
DellEMC(conf)# router bgp 65535
DellEMC(conf-router_bgp)# neighbor 20.20.20.1 remote-as 20
DellEMC(conf-router_bgp)# neighbor 20.20.20.1 no shutdown
DellEMC(conf-router_bgp)#exit
DellEMC(conf)#

The following example shows verifying the BGP configuration using the show running-config bgp command..

DellEMC#show running-config bgp
!
router bgp 65535
 neighbor 20.20.20.1 remote-as 20
 neighbor 20.20.20.1 no shutdown
DellEMC#

Examples of the show ip bgp Commands

The following example shows the show ip bgp summary command output.

R2#show ip bgp summary
BGP router identifier 1.1.1.1, local 65535
BGP local RIB : Routes to be Added 0, Replaced 0, Withdrawn 0
1 neighbor(s) using 40960 bytes of memory

Neighbor        AS            MsgRcvd  MsgSent     TblVer  InQ  OutQ Up/Down  State/Pfx
20.20.20.1      20                 0        0          0    0     0 00:00:00 0

For the router’s identifier, Dell EMC Networking OS uses the highest IP address of the Loopback interfaces configured. Because Loopback interfaces are virtual, they cannot go down, thus preventing changes in the router ID. If you do not configure Loopback interfaces, the highest IP address of any interface is used as the router ID.

To view the status of BGP neighbors, use the show ip bgp neighbors command in EXEC Privilege mode as shown in the first example. For BGP neighbor configuration information, use the show running-config bgp command in EXEC Privilege mode as shown in the second example.

NOTE The showconfig command in CONFIGURATION ROUTER BGP mode gives the same information as the show running-config bgp command.

The following example displays two neighbors: one is an external internal BGP neighbor and the second one is an internal BGP neighbor. The first line of the output for each neighbor displays the AS number and states whether the link is an external or internal (shown in bold).

The third line of the show ip bgp neighbors output contains the BGP State. If anything other than ESTABLISHED is listed, the neighbor is not exchanging information and routes. For more information about using the show ip bgp neighbors command, refer to the Dell EMC Networking OS Command Line Interface Reference Guide.

The following example shows the show ip bgp neighbors command output.

DellEMC#show ip bgp neighbors
BGP neighbor is 20.20.20.1, remote AS 20, external link
  BGP remote router ID 1.1.1.1
  BGP state ESTABLISHED, in this state for 00:05:22
  Last read 00:00:00, Last write 00:00:07
  Hold time is 90, keepalive interval is 30 seconds
  Received 18 messages, 0 in queue
     7 opens, 6 notifications, 0 updates
     5 keepalives, 0 route refresh requests
  Sent 26 messages, 0 in queue
     7 opens, 0 notifications, 0 updates
     19 keepalives, 0 route refresh requests

  Route refresh request: received 0, sent messages 0
  Minimum time between advertisement runs is 30 seconds
  Minimum time before advertisements start is 0 seconds

   For address family: IPv4 Unicast
  BGP local RIB : Routes to be Added 0, Replaced 0, Withdrawn 0
  InQ : Added 0, Replaced 0, Withdrawn 0
  OutQ : Added 0, Withdrawn 0
  Allow local AS number 0 times in AS-PATH attribute
  Prefixes accepted 0, withdrawn 0 by peer, martian prefixes ignored 0
  Prefixes advertised 0, denied 0, withdrawn 0 from peer

  Connections established 0; dropped 0
  Last reset never
        No active TCP connection

Welcome

Welcome to Dell

Dell Configuration Guide for the S4048–ON System 9.14.2.6

Enabling BGP

Example configuration steps to enable BGP

Rate this content