backup-selection (Protocols IS-IS)
Syntax
backup-selection {
destination prefix {
interface (interface-name| all){
admin-group {
exclude [ group-name ];
include-all [ group-name ];
include-any [ group-name ];
preference [ group-name ];
}
bandwidth-greater-equal-primary;
dest-metric (highest | lowest);
downstream-paths-only;
metric-order [ root dest ];
node {
exclude [ node-address ];
preference [ node-address ];
}
node-tag {
exclude [ route-tag ];
preference [ route-tag ];
}
protection-type (link | node | node-link);
root-metric (highest | lowest);
evaluation-order [ admin-group srlg bandwidth protection-type
node node-tag metric ] ;
}
}
}
Hierarchy Level
[edit logical-systems logical-system-name routing-options],
[edit logical-systems logical-system-name routing-instances instance-name routing-options],
[edit routing-instances instance-name routing-options],
[edit routing-options]
Release Information
Statement introduced in Junos OS Release
14.1.
Description
Define backup selection policies, per prefix per
primary next-hop interface, to enforce loop-free alternate (LFA) selection
based on admin-group, srlg, bandwidth, protection-type, node, node-tag,
and metric attributes of the backup path.
The remaining statements are explained separately. See CLI Explorer.
Options
destination prefix—Define the backup selection policy for a particular
destination prefix or for all the prefixes. The prefix is the destination prefix name and prefix length. You can specify
0/0 for the IPv4 least-specific prefix or 0::0/0 for the IPv6 least-specific
prefix.
interface—Define the
backup selection policy for a specific primary next hop.
interface-name— Name of the primary next-hop interface.
bandwidth-greater-equal-primary— Allow the selection of the backup next hop only if
the bandwidth is greater than or equal to the bandwidth of the primary
next hop.
dest-metric (highest | lowest)—Specifiy the metric from the one-hop neighbor or from the remote
router such as an RSVP backup label-switched-path (LSP) tail-end router
to the final destination.
highest— Select the
backup path that has the highest destination metric.
lowest— Select the
backup path that has the lowest destination metric.
downstream-paths-only— Select the backup path that is a downstream path to the destination.
evaluation-order [ admin-group srlg bandwidth
protection-type neighbor neighbor-tag metric ]—Control the order and the criteria of evaluating the backup
path. The default order of evaluation is admin-group, srlg, bandwidth,
protection-type, neighbor, neighbor-tag, and metric.
NoteFor the explicitly configured evaluation order, only the
listed attributes influence the selection of the backup path.
metric-order [ root dest ]— Specify the order of preference of the root and the destination
metric during the backup path selection. The preference order can
be:
[root dest] — Backup path selection or
preference is first based on the root-metric criteria. If the criteria
of all the root-metric is the same, then the selection or preference
is based on the dest-metric.
[dest root] — Backup path selection or
preference is first based on the dest-metric criteria. If the criteria
of all the dest-metric is the same, then the selection is based on
the root-metric.
NoteBy default, backup paths with lower destination metric
criteria are selected or preferred. If the criteria is the same, then
the lowest root metric criteria is preferred or selected.
root— The metric to
a one-hop neighbor or a remote router.
dest— The metric from
a one-hop neighbor or remote router to the final destination.
protection-type (link | node | node-link)—Specify the required protection type of the backup
path.
NoteIf no protection-type is configured, then by default the
first best path that matches all the other criteria is executed.
link— Select the backup
path that provides link protection.
node— Select the backup
path that provides node protection.
node-link— Allow either
node or link protection LFA where node-protection LFA is preferred
over link-protection LFA.
root-metric (highest | lowest)—Specify the metric to the one-hop neighbor or to the remote
router such as an RSVP backup label-switched-path (LSP) tail-end router.
highest— Select the
highest root metric.
lowest— Select the
lowest root metric.
srlg (loose | strict)—Define the backup selection to either allow or reject the common
shared risk link groups (SRLGs) between the primary link and any link
in the backup path.
loose— Allow the backup
path that has common srlgs between the primary link and any link in
the backup path. A backup path with a fewer number of srlg collisions
is preferred.
strict— Reject the
backup path that has common srlgs between the primary link and each
link in the backup path.
node—Define a list
of loop-back IP addresses of the adjacent nodes to either prefer or
exclude in the backup path selection. The node can be a local (adjacent
router) node, remote node, or any other router in the backup path.
NoteThe nodes are identified through the TE-router-ID TLV
advertised by a node in the LSP.
exclude [ node-address ]— Specify the list of nodes to be excluded. The backup
path that has a router from the list is not selected as the loop-free
alternative or backup next hop.
node-address— Name
of one or more nodes to be excluded during backup path selection.
preference [ node-address ]— Define an ordered set of nodes to
be preferred. The backup path having the leftmost node is selected.
node-address— Name
of one or more nodes to be preferred in the backup path selection.
node-tag—Define per-neighbor
policy to either prefer or exclude a backup path.
NoteThis statement identifies a group of nodes in the network
based on criteria such as the same neighbor tag values for all PE
nodes. This is implemented using IS-IS admin-tags.
exclude [ node-address ]— Specify the list of nodes to be excluded. The backup
path that has a router from the list is not selected as the loop-free
alternative or backup next hop.
node-address— Name
of one or more nodes to be excluded during backup path selection.
preference [ node-address ]— Define an ordered set of nodes to
be preferred. The backup path having the leftmost node is selected.
node-address— Name
of one or more nodes to be preferred in the backup path selection.
The remaining statements are explained separately. See CLI Explorer.
Required Privilege Level
routing—To view this statement in the
configuration.
routing-control—To add this statement to the configuration.
