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segment-list

Syntax

Hierarchy Level

Description

Specify an name to identify the segment routing list (used in traffic engineering policy) and the explicit path for source routing label switched path (LSPs) to traverse through traffic engineering segments. The segment list is essentially a stack of segment identifiers.

Starting in Junos OS release 19.1R1 for MX and PTX Series routers, you can enable a translation service to translate next-hop IP addresses into the corresponding segment identifier (SID) labels. The translation service keeps track of the node reached at each hop.

When configured, the segment-list of a segment routing traffic engineering (SR-TE) LSP accepts IP addresses for all the hops along the path. These IP addresses can be either the loopback address of a node, or the IP address of a link, as identified by the node-type. When auto-translation is enabled, next hop IP addresses are automatically translated to corresponding SIDs using the translation service. A retry rate can be set for the retry timer at the source-packet-routing hierarchy level.

Note:

The segment list enables BGP and static segment routing LSP to steer traffic based on segment routing policies. When a segment list is used by the protocol BGP, the BGP protocol validates these segment identifiers and selects valid segments for traffic engineering.

Options

name

Specify a name to identify a SR-TE segment-list.

Note:

The combined length of tunnel-name and LSP name must not exceed 53 characters for per-path telemetry to work.

<hop-name>

Indicates the next hop in the segment routing traffic engineering policy (SR-TE).

  • ip-address—Specify the IP address of the hop. For a segment-list to be used by a non-colored segment routing LSP, the first hop must specify an IP address.

  • label—Specify the SID label of the hop in a segment routing traffic engineering segment list. In static segment routing LSPs, the source routing path uses the segment list only if the second to Nth hop specifies segment identifiers (SID) labels.

    Note:

    The range is from 0 to 1,048,576 and is applies to BGP and static segment routing LSPs.

  • label-type—Use with the option below to indicate that the specified address is the IP address of the node, for example, its loopback address, as opposed to that of a link.

    • node—Hops that have been specified as node are translated to a prefix SID, which can be either a node SID or an anycast SID depending on the type of hop IP address. IP addresses not identified as node are consider to be a link.

    Note:

    If the first hop is a node, for LSP resolution to work correctly, inherit-label-nexthops must be enabled at either source-packet-routing hierarchy level, or at the relevant segment-list hierarchy level.

  • loose | strict—IP hops specified using router IDs in the sequence can be strict or loose hops. A strict hop must be directly connected to the previous node in the sequence. A loose hop is not necessarily directly connected to the previous node.

    Note:

    You can specify only router IDs as loose or strict hop constraints. Labels and other IP addresses are not supported as loose or strict hop constraints in Junos OS Release 19.2R1-S1.

srv6 Specify SRv6 TE segment list.
srv6-sid Indicates the SID for SRv6 segment-list in the form of IPv6 address.
Note:

An SRv6 segment-list can only have SRv6 SID which is a node SID (either the end-sid or end-x sid of the transit and end-sid of the egress nodes). Therefore, you need to correctly configure the last SRv6 SID in the segment-list as the end-sid of the egress PE.

auto-translate

This option must be enabled before a given segment list can use IP addresses instead of SIDs for any hop other than the first hop. In addition, all hops in the segment list must have IP addresses. If any hops on the list have both an IP address and a label configured, the label will be retained. Link addresses are only translated into labels if the preceding node advertises an adjacency SID for the address (otherwise translation fails).

Note:

In Junos OS Release 19.1R1, for auto-translate to work for OSPF, RSVP for segment routing must be enabled on all participating interfaces.

  • protected—(Optional) Enable this option to ensure the adjacency SID is eligible to have a backup path, and that a B-flag is set in adjacency SID advertisements. Note that unless mandatory is also selected, the choice succeeds regardless.

    • mandatory—(Optional) Enable this option to have translation fail if any unprotected links are found in the hop-list.

  • unprotected—(Optional) Enable this option to ensure that no backup path is calculated for a specific adjacency SID, and that a B-flag is not set in adjacency SID advertisements. Note that unless mandatory is also selected, the choice succeeds regardless.

  • mandatory—(Optional) Enable this option to have translation fail if any protected links are found the hop-list.

compute

(Optional) Enable use of explicit paths specified in segment list for path computation.

inherit-label-nexthops

Inherit label next hops for first hop in this segment list that have both IP address and label configured in the first hop.

You can configure the inherit-label-nexthops statement globally or individually for each segment list.

The inherit-label-nexthops statement takes effect only when the segment list first hop has both IP address and SID label present.

If the inherit-label-nexthops is not configured at the [edit protocols source-packet-routing segment-list] hierarchy, and the first hop in the segment list has both IP address and label specified, the default behavior is to use the IP address.

The remaining statements are explained separately. Search for a statement in CLI Explorer or click a linked statement in the Syntax section for details.

Required Privilege Level

routing—To view this statement in the configuration.

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

Release Information

Statement introduced in Junos OS Release 17.4R1.

ip-address statement introduced in Junos OS Release 18.1R1 on MX Series routers.

inherit-label-nexthops, node-type, and auto-translate statements introduced in Junos OS Release 19.1R1 on MX Series routers.

dynamic statement introduced in Junos OS Release 19.2R1 on all platforms.

compute, loose, and strict statements introduced in Junos OS Release 19.1R1-S1 on MX Series routers.

srv6-sid statement introduced in Junos OS Release 21.3R1.