17-104 Riverstone Networks RS Switch Router User Guide Release 8.0
Traffic Engineering MPLS Configuration
The mpls show interface command shows the interfaces configured on an RS and the administrative group, if
any, that is applied to an interface. For example, in the following output the administrative group sector1 is applied to
the interfaces R2R3 and R2R1b:
17.7.2 Constrained Shortest Path First
An ingress LSR uses the information in the traffic engineering database (TED) to calculate its LSPs across the network.
The constrained shortest path first (CSPF) algorithm is a modification of the OSPF and IS-IS shortest path first
calculation. With CSPF, nodes and links for an LSP are accepted or rejected based on resource availability or on
whether administrative group or policy constraints are met. The result is an explicit route that provides the shortest
path through the network that meets certain constraints. The explicit route, comprised of a sequence of LSR addresses,
is passed to the signaling protocol to deliver the path information to each LSR in the LSP.
The CSPF algorithm takes into account link-state and network state information from the TED, as well as the following
LSP attributes:
•bandwidth
•hops
•administrative group
•setup and hold priority
•strict or loose explicit route
To enable CSPF on RS routers:
1. If OSPF is the IGP, enable traffic engineering extensions for OSPF with the ospf set
traffic-engineering on command. If IS-IS is the IGP, enable traffic engineering extensions
for IS-IS with the isis set traffic-engineering enable command.
Note Traffic engineering with OSPF as the IGP requires support for opaque LSAs
(defined by RFC 2370). This support is enabled by default on the RS, but can be
disabled with the ospf set opaque-capability off CLI command. If you
are enabling traffic engineering extensions for OSPF, make sure that opaque LSA
support has not been disabled.
2. Configure the dynamic LSP, as described in Section17.5.3, "Configuring an Explicit LSP." Do not
specify the no-cspf parameter with the mpls create label-switched-path or mpls set
label-switched-path commands.
rs# mpls show interface all
Interface State Administrative groups
lo Up <none>
lo Up <none>
R2R3 Up sector1
R2R1 Up <none>
R2R1b Up sector1