Is-is shortcuts over an lsp tunnel, Creating ospf shortcuts over an lsp tunnel – Brocade Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide (Supporting R05.6.00) User Manual
Page 618
594
Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide
53-1003031-02
Using traffic-engineered LSPs within an AS
5
The cost of the LSP is the user-configured metric for the LSP. When there is no user-configured
metric, the underlying IP cost of the LSP is used. For example, when the IP cost of the best
underlying path between two routers is 2, and there is an LSP configured between these two
routers, the cost of the LSP is 2. Once an LSP is used as a next hop for a destination, the cost of the
LSP can be used to calculate other destinations that can use the LSP egress node as next hop. This
allows traffic for addresses downstream from the LSP egress node (including prefixes of the egress
node) to use the LSP shortcut.
When OSPF is already using an LSP tunnel route to an Area Border Router (ABR), all inter-area
routes through that ABR use the LSP as the next hop, provided there are no other better paths to
the destination (paths through other ABRs). An LSP to a destination outside an area is not used by
OSPF in the calculation of inter-area routes.
Only signaled LSPs can be used as OSPF shortcuts. RSVP packets, used to establish and maintain
signaled LSPs, are never forwarded into LSP tunnels.
Refer to
“Creating OSPF shortcuts over an LSP tunnel”
IS-IS shortcuts over an LSP tunnel
Refer to
597 for details about creating IS-IS shortcuts over an LSP tunnel.
Creating OSPF shortcuts over an LSP tunnel
This feature allows the user to forward traffic to destinations within an OSPF routing domain
through an LSP tunnel, which optimizes available bandwidth by choosing LSPs where multiple
paths exist to the same OSPF destination. When an LSP is configured as an OSPF shortcut, OSPF
includes the LSP in the SPF calculation. When OSPF determines that the LSP shortcut is the best
path to a destination, it adds a route to the IP routing table, specifying the LSP tunnel interface as
the outbound interface, along with the cost of the LSP. Only LSPs configured to router ID are
considered as shortcuts. When the LSP goes down or is administratively disabled, or the shortcuts
ospf command is removed from the configuration, the LSP tunnel route is removed from the main
routing table.
LSPs used for this feature must originate and terminate within the same OSPF area. When
configured, OSPF directs routes that are reachable from the egress router of a shortcut-enabled
LSP to an LSP tunnel as the outgoing interface.
To configure this feature, point the LSP to the router ID of the egress router where traffic is
forwarded. The user must also configure the LSP with the shortcuts ospf command.
The following configuration of LSP “tunnel1” specifies the egress router with a router ID of 10.2.2.2
and enables it for OSPF shortcuts.
Brocade(config)# router mpls
Brocade(config-mpls)# lsp tunnel1
Brocade(config-mpls-lsp)# to 10.2.2.2
Brocade(config-mpls-lsp)# shortcuts ospf
Brocade(config-mpls-lsp)# enable
Syntax: [no] shortcuts ospf