Brocade Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide (Supporting R05.6.00) User Manual
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Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide
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MPLS Fast Reroute using facility backup over a bypass LSP
1
•
The protected LSP
The specification of a bypass LSP includes manual entry of a list of interfaces at the PLR that
cannot make up the bypass LSPs own route. These excluded interfaces are the interfaces that the
protected LSPs traverse. Therefore, from the standpoint of the bypass LSP, the protected interfaces
on the PLR are called excluded interfaces. (When the protected interfaces were included in the
backup path rather than excluded from the backup path, then the interfaces would be protecting
themselves — a logical contradiction.)
In facility backup, the linkage of the protected LSP to the bypass LSP is established by the following
events:
•
The request from an MPLS LSP for facility backup: At the ingress node (R1 in
, for
example), LSP 1 is configured to request facility backup.
•
The intersection of an MPLS LSP and a bypass LSP: When an LSP requesting facility backup
traverses an interface on a router (R2
) with a bypass LSP that has LSP 1’s outbound
interface in its user-specified list of excluded interfaces, then LSP 1 can become protected at
that point, and R2 is a PLR.
The bypass LSP identifies the interfaces to protect in the command that creates the bypass
LSP. In
, LSP 1 and LSP 2 enter R2. The outbound interfaces for these LSPs are e
1/1 and e1/2. To provide protection to LSP 1 and LSP 2, the interfaces e 1/1 and e 1/2 are
listed as exclude interfaces in the configuration of the bypass LSP.
In complex topologies, an interface can have multiple bypass LSPs protecting it. For example,
the LSPs that traverse an interface might have destinations that make a single merge point
impossible, so multiple bypass LSPs would be needed in this case to support different LSPs.
Therefore, more than one bypass LSP can have the same interface in its list of exclude
interfaces.
NOTE
The bypass LSP must have the bandwidth capacity to carry the traffic of all of its assigned
LSPs. Before a candidate LSP chooses a bypass LSP on a given interface, software determines
whether the bypass LSP can reserve sufficient bandwidth for the candidate LSP.
NOTE
In the current release, BFD for facility backup FRR LSP is not supported. The system returns an
error when the user tries either to enable BFD for facility backup for an LSP or to set
facility-backup mode for an LSP with BFD enabled. Further, the BFD option is not available in
the bypass LSP configuration context.