RSVP-TE LSP Shortcut for IGP Resolution
Page 132 7450 ESS MPLS Guide
Note that the igp-shortcut option under the LSP name governs the use of the LSP with both the
rsvp-shortcut and the advertise-tunnel-link options in IGP. The interactions of these options are
summarized in Table 8:
LDP Forwarding over IGP Shortcut
The user can enable LDP FECs over IGP shortcuts by configuring T-LDP sessions to the
destination of the RSVP LSP. In this case, LDP FEC is tunneled over the RSVP LSP, effectively
implementing LDP-over-RSVP without having to enable the ldp-over-rsvp option in OSPF or IS-
IS. The ldp-over-rsvp and igp-shortcut options are mutually exclusive under OSFP or IS-IS.
Table 8: Impact of LSP level configuration on IGP shortcut and forwarding adjacency features
LSP level configuration Actions with IGP Shortcut
Feature
Actions with Forwarding
Adjacency Feature
igp-shortcut Tunnel is used in main SPF, but is
not used in LFA SPF
Tunnel is advertised as p2p link if
it has best LSP metric, is used in
main SPF if advertised, but is not
used in LFA SPF
igp-shortcut lfa-protect Tunnel is used in main SPF, and is
used in LFA SPF
Tunnel is advertised as p2p link if
it has best LSP metric, is used in
main SPF if advertised, and is used
in LFA SPF regardless if it is
advertised or not
igp-shortcut lfa-only Tunnel is not used in main SPF, but
is used in LFA SPF
Tunnel is not advertised as p2p
link, if not used in main SPF, but is
used in LFA SPF
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