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send (add-path)

 

Syntax

Hierarchy Level

Release Information

Statement introduced in Junos OS Release 11.3.

Support for range from 2 through 20 (for BGP) introduced in Junos OS Release 14.1.

multipath option introduced in Junos OS Release 16.1R2.

Support for 64 BGP add-paths introduced in Junos OS Release 18.4R1 for the MX Series.

include-backup-path and path-selection-mode options introduced in Junos OS Release 18.4R1 for the MX Series and PTX Series.

Description

Enable advertisement of multiple paths to a destination, instead of advertising only the active path.

Options

include-backup-path Configure the number of backup paths that BGP must advertise. Do not configure this option if you have configured all-paths at the [edit protocols bgp group name family name add-path send] hierarchy level.

Range: 1 through 2

multipath Restrict BGP add-path to advertise contributor multiple paths only. Advertising all available multiple paths might result in a large overhead of processing on device memory. Selective advertising of multiple paths facilitates Internet service providers and data centers that use route reflectors to build in-path diversity in IBGP. You can limit and configure up to six prefixes that the BGP multipath algorithm selects. You cannot configure both multipath and path-selection-mode at the same time.

For example, if a routing device has four paths to a destination in its routing table and is configured to advertise up to two paths, only contributor paths for load balancing are chosen. The best contributor path is the active path and BGP advertises this path by default. The second best contributor path is selected and this process is repeated until the specified number of paths is reached; in this case, two additional paths to the same destination are selected for load balancing.

path-count numberSpecify the number of paths to a destination to advertise.

Suppose a routing device has in its routing table four paths to a destination and is configured to advertise up to three paths (add-path send path-count 3). The three paths are chosen based on path selection criteria. That is, the three best paths are chosen in path-selection order. The best path is the active path. This path is removed from consideration and a new best path is chosen. This process is repeated until the specified number of paths is reached.

Range: 2 through 64

Default: 1

path-selection-mode Specify whether BGP can advertise all the available paths or only the equal-cost paths. BGP can advertise up to 64 add-path routes and a second best ECMP path as a backup in addition to the multiple ECMP paths. You cannot configure both multipath and path-selection-mode at the same time.

Values:

  • all-paths—Specify the total number of add-path routes to advertise. BGP advertises all the paths that are allowed by the configured prefix policy and the maximum paths configured using the path-count option.

  • equal-cost-paths—Specify the equal-cost paths to advertise. You can configure either this option or the multipath option; they are mutually exclusive.

prefix-policy policy-names Specify the name of a policy (or a set of policies) configured at the [edit policy-options] hierarchy level to filter the paths to a destination to advertise.

Prefix policies enable you to filter routes on a router that is configured to advertise multiple paths to a destination. Prefix policies can only match prefixes. They cannot match route attributes, and they cannot change the attributes of routes.

The add-path prefix-policy allows up to 64 BGP add-paths to be advertised for a subset of prefixes that match the add-path prefix-policy. To enable this feature for a prefix, the add-path prefix-policy term matching the prefix should have a new then action to set add-path send-count <2...64>. This new action is not applicable if the policy-statement containing it is used in any place other than add-path prefix-policy.

Range: 2 through 64 (for BGP)

Note

This range is applicable only under prefix-policy add-path.

Required Privilege Level

routing—To view this statement in the configuration.

routing-control—To add this statement to the configuration.