Alcatel-Lucent 7450 Manual page 260

MPLS Commands
fast-reroute
Syntax fast-reroute frr-method
no fast-reroute
Context config>router>mpls>lsp
Description
This command creates a pre-computed detour LSP from each node in the path of the LSP. In case of
failure of a link or LSP between two nodes, traffic is immediately rerouted on the pre-computed
detour LSP, thus avoiding packet-loss.
When fast-reroute is enabled, each node along the path of the LSP tries to establish a detour LSP as
follows:
Fast reroute is available only for the primary path. No configuration is required on the transit hops of
the LSP. The ingress router will signal all intermediate routers using RSVP to set up their detours. TE
must be enabled for fast-reroute to work.
If an LSP is configured with fast-reroute frr-method specified but does not enable CSPF, then
neither global revertive nor local revertive will be available for the LSP to recover.
The no form of the fast-reroute command removes the detour LSP from each node on the primary
path. This command will also remove configuration information about the hop-limit and the
bandwidth for the detour routes.
The no form of fast-reroute hop-limit command reverts to the default value.
Default no fast-reroute — When fast-reroute is specified, the default fast-reroute method is one-to-one.
Parameters
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• Each upstream node sets up a detour LSP that avoids only the immediate downstream node, and
merges back on to the actual path of the LSP as soon as possible.
If it is not possible to set up a detour LSP that avoids the immediate downstream node, a detour
can be set up to the downstream node on a different interface.
• The detour LSP may take one or more hops (see hop-limit) before merging back on to the main
LSP path.
• When the upstream node detects a downstream link or node failure, the ingress router switches
traffic to a standby path if one was set up for the LSP.
one-to-one — In the one-to-one technique, a label switched path is established
which intersects the original LSP somewhere downstream of the point of link or
node failure. For each LSP which is backed up, a separate backup LSP is facility
— This option, sometimes called many-to-one, takes advantage of the MPLS label
stack. Instead of creating a separate LSP for every backed-up LSP, a single LSP is
created which serves to backup up a set of LSPs. This LSP tunnel is called a bypass
tunnel.
The bypass tunnel must intersect the path of the original LSP(s) somewhere
downstream of the point of local repair (PLR). Naturally, this constrains the set of
LSPs being backed-up via that bypass tunnel to those that pass through a common
downstream node. All LSPs which pass through the PLR and through this
common node which do not also use the facilities involved in the bypass tunnel are
candidates for this set of LSPs.
7450 ESS MPLS Guide