Riverstone Networks WICT1-12 17.7.3 IGP Shortcuts,

Riverstone Networks RS Switch Router User Guide Release 8.0 17-119
MPLS Configuration Traffic Engineering
17.7.3 IGP Shortcuts
Link-state IGPs, such as IS-IS and OSPF, use shortest path calculations to produce destination-first hop entries in the
routing table. With normal hop-by-hop routing, the first hop is a physical interface on the router. A logical interface,
which represents an explicit path LSP, can also be installed in the routing table to be used by the IGP as the first hop
to a specified destination. Thus, the LSP is used as a “shortcut” to a specific destination in the network.
Using IGP shortcuts provides the following benefits:
•control of traffic to destinations that do not support MPLS LSPs
•allows LSPs to be deployed on a regional basis
IGP shortcuts can be enabled on a per-router basis (it is disabled by default). When IGP shortcuts are enabled, each
router maintains a list of IGP shortcuts that originate at the local router and the ID of the router at the opposite end of
the shortcut. Traffic to nodes that are at the tail end of a shortcut and to nodes that are downstream from the end of a
shortcut will flow over the shortcut.
To enable IGP shortcuts on RS routers that use OSPF as the IGP:
To enable IGP shortcuts on RS routers that use IS-IS as the IGP:
Available BW [priority]:
[0] 12 Mbps [1] 12 Mbps
[2] 12 Mbps [3] 12 Mbps
[4] 12 Mbps [5] 12 Mbps
[6] 12 Mbps [7] 12 Mbps
To: 1212.1212.1212.0e, Local: 186.1.1.26, Remote: 186.1.1.12
Color: 0x8
Static BW: 20 Mbps
Reservable BW: 20 Mbps
Available BW [priority]:
[0] 20 Mbps [1] 20 Mbps
[2] 20 Mbps [3] 20 Mbps
[4] 20 Mbps [5] 20 Mbps
[6] 20 Mbps [7] 20 Mbps
ip-router global set install-lsp-routes on
ospf set igp-shortcuts on
ip-router global set install-lsp-routes on
isis set igp-shortcuts enable