Using Lsp Relative Metric With Igp Shortcut - Alcatel-Lucent 7450 Manual

Table 7: RSVP LSP Role As Outcome of LSP level and IGP level configuration options
igp-shortcut dis- None
abled / ldp-over-
rsvp enabled
igp-shortcut dis- None
abled / ldp-over-
rsvp disabled
The resolution and forwarding of IPv6 prefixes to IPv4 IGP shortcuts is not supported.
The no form of this command disables the resolution of IGP routes using RSVP shortcuts.

Using LSP Relative Metric with IGP Shortcut

By default, the absolute metric of the LSP is used to update the SPF tree when the user enables
IGP shortcut by configuring the rsvp-shortcut option in IGP. The absolute metric is the operational
metric of the LSP populated by MPLS in the Tunnel Table Manager (TTM). This corresponds to
the cumulative IGP-metric of the LSP path returned by CSPF or the static admin metric value of
the LSP if the user configured one using the config>router>mpls>lsp>metric command. Note
that MPLS populates the TTM with the maximum metric value of 16777215 in the case of a CSPF
LSP using the TE-metric and a non-CSPF LSP with a loose or strict hop in the path. A non-CSPF
LSP with an empty hop in the path definition returns the IGP cost for the destination of the LSP.
The user enables the use of the relative metric for an IGP shortcut with the following new CLI
command:
config>router>mpls>lsp>igp-shortcut relative-metric [offset]
IGP will apply the shortest IGP cost between the endpoints of the LSP plus the value of the offset,
instead of the LSP operational metric, when computing the cost of a prefix which is resolved to the
LSP.
The offset value is optional and it defaults to zero. An offset value of zero is used when the
relative-metric option is enabled without specifying the offset parameter value.
The minimum net cost for a prefix is capped to the value of one (1) after applying the offset:
Prefix cost = max(1, IGP cost + relative metric offset)
Note that the TTM continues the show the LSP operational metric as provided by MPLS. In other
words, applications such as LDP-over-RSVP (when IGP shortcut is disabled) and BGP and static
route shortcuts will continue to use the LSP operational metric.
7450 ESS MPLS Guide
IGP Instance level configurations
None None
None None
MPLS and RSVP
None None
None None
LDP-over-
RSVP
None
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