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BGP Auto-Discovered Neighbors

SUMMARY Use BGP auto-discovered neighbor to configure BGP peering by interface rather than by specifying remote or local neighbor IP addresses.

Understanding BGP Auto-discovered Neighbor

SUMMARY Use BGP auto-discovered neighbor to configure BGP peering by interface rather than by specifying remote or local neighbor IP addresses.

To establish a BGP session between routers, you must explicitly configure BGP groups and peers by address. BGP peering sessions require that you identify source and destination IP addresses for endpoints of the TCP communication. Therefore, explicitly configuring these addresses is an obstacle to network scale-out and an opportunity for misconfiguration.

To streamline your BGP configuration, we have removed the need to configure per-peer address from BGP. Use BGP auto-discovered neighbor to configure BGP peering by interface rather than by specifying remote or local neighbor IP addresses. This includes use of implicit or protocol mechanisms to discover the IP addresses for use in the TCP peering sessions.

Figure 1: BGP Auto-discovered Neighbor BGP Auto-discovered Neighbor
Note:

Peering behavior and address usage must be explicitly configured to avoid peering changes based on interface address changes due to configuration or address validity (for example, IPv6 Duplicate Address Detection (DAD)).

BGP determines the address families to peer over based on the configuration. The peering sessions come up based on availability of the interface addresses for the determined families. The peer link-local address is discovered using IPv6 neighbor discovery (RFC4861) and creates a BGP session toward that neighbor. A link-local address is generated even when IPv6 interfaces have no addresses configured.

Note:

You must enable IPv6 neighbor discovery for this feature to work.

Benefits of BGP Auto-discovered Neighbor

  • Simplifies IGP deployment to a single-hop external BGP (EBGP)

  • Configures neighbors by interfaces and interface ranges instead of by IP addresses

  • Minimizes configuration on both sides with dynamic-neighbor groups

Example: Configuring BGP Auto-discovered Neighbor

SUMMARY This example shows how to configure BGP Auto-discovered Neighbor.

Overview

Starting in Junos OS Release 21.1R1, we support BGP auto-discovered neighbors using IPv6 Neighbor Discovery Protocol (ND). This feature allows BGP to create peer neighbor sessions using link-local IPv6 addresses of directly connected neighbor routers. You need not specify remote or local neighbor IP addresses.

Topology

The following figure shows a simplified sample topology.

Requirements

This example uses the following hardware and software components:

MX Series routers

Junos OS Release 21.1R1 or later

Configuration

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, and then copy and paste the commands into the CLI at the [edit] hierarchy level.

VM1

VM2

Leaf 1

Leaf 2

Spine 1

Spine 2

Configuring VM1

To configure BGP auto-discovered neighbor, perform the following steps on VM1:

  1. Configure the device interfaces.

  2. Create the loopback interface and configure the IP address.

  3. Enable routing policies.

  4. Configure the autonomous system (AS) number

  5. Apply the per-packet policy to enable load balancing of traffic and ECMP.

  6. Configure BGP to establish internal and external peering sessions.

  7. If you are done configuring the device, commit the configuration.

Results

From configuration mode, confirm your configuration by entering the show interfaces, show protocols, show policy-options, and show routing-options commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

Verification

Confirm that the configuration is working properly.

Verifying Auto-discovered neighbors

Purpose

Verify the auto-discovered BGP neighbors.

Action

From operational mode, run the show bgp summary auto-discovered command

On Leaf1

On Spine1

Meaning

The output shows the summary of auto-discovered bgp neighbors. You can see the number of auto-discovered peers and its details.

Verifying BGP Auto-discovered Peers

Purpose

Verify the auto-discovered BGP neighbors.

Action

From operational mode, run the show bgp neighbor auto-discovered command.

On Leaf1

On Spine1

Meaning

The output shows information about the auto-discovered BGP neighbors.