MPLS and RSVP
7210 SAS M, T, X, R6, Mxp MPLS Configuration Guide Page 117
Once the primary path of the LSP is set up and is operationally up, any subsequent changes to the
SRLG group membership of an interface the primary path is using would not be considered by the
MPLS/RSVP task at the PLR for bypass/detour association until the next opportunity the primary
path is re-signaled. The path may be re-signaled due to a failure or to a make-before break operation.
Make-before break occurs as a result of a global revertive operation, a timer based or manual re-
optimization of the LSP path, or a user change to any of the path constraints.
Once the bypass or detour path is setup and is operationally UP, any subsequent changes to the SRLG
group membership of an interface the bypass/detour path is using would not be considered by the
MPLS/RSVP task at the PLR until the next opportunity the association with the primary LSP path is
re-checked. The association is re-checked if the bypass path is re-optimized. Detour paths are not re-
optimized and are re-signaled if the primary path is down.
Enabling or disabling srlg-frr only takes effect after LSP paths are resignaled. This can be achieved
by shutting down and re-enabling MPLS. Another option is using the tools perform router mpls
resignal command. However, note that while the latter might be less service impacting, only
originating LSPs can be resignaled with the tools command. If also local transit and bypass LSPs are
to be resignaled, the tools command must be executed on all ingress nodes in the network. The same
might be locally achieved by disabling and enabling using the configure router mpls dynamic-
bypass command, but this can trigger the LSP to go down and traffic loss to occur in case detour or
bypass LSP is in use.
An RSVP interface can belong to a maximum of 64 SRLG groups. The user configures the SRLG
groups using the command config>router>mpls>srlg-group. The user configures the SRLG groups
an RSVP interface belongs to using the srlg-group command in the config>router>mpls>interface
context.
The no form of the command reverts to the default value.
Default no srlg-frr
Parameters strict — Specifies the name of the SRLG group within a virtual router instance.
Values no slr-frr (default)
srlg-frr (non-strict)
srlg-frr strict (strict)
srlg-group
Syntax srlg-group group-name {value group-value}
no srlg-group group-name
Context config>router>mpls
Description This command is used to define shared risk link groups (SRLGs). An SRLG group represents a set of
interfaces which could be subject to the same failures or defects and thus share the same risk of
failing.
RSVP interfaces must be explicitly assigned to an SRLG group. SRLG groups must be defined in the
config>router>mpls context before they can be assigned to an RSVP interface. Two different SRLG
group names cannot share the same value. Once an SRLG group has been bound to an MPLS
interface, its value cannot be changed until the binding is removed.
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