Cisco Cisco IOS Software Release 12.0(13)S7
MPLS Safe Label Reuse After Router Restart
Restrictions for MPLS Safe Label Reuse
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Cisco IOS Release 12.0(32)SY
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Restrictions for MPLS Safe Label Reuse
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This feature does not track the use and reuse of statically assigned labels.
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If the steady-state requirement for MPLS labels exceeds half the configured label space, MPLS
convergence might be delayed following a non-stateful switchover (SSO) restart. The pool of
available labels could be insufficient to meet the demand until the safe-to-reuse timer expires.
convergence might be delayed following a non-stateful switchover (SSO) restart. The pool of
available labels could be insufficient to meet the demand until the safe-to-reuse timer expires.
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On rare occasions with redundant platforms, the persistent data required to prevent unsafe label
reuse following a restart on the Route Processor (RP) selected as the active RP might not be an
up-to-date record of label use prior to the restart. This could occur, if prior to the restart, the:
reuse following a restart on the Route Processor (RP) selected as the active RP might not be an
up-to-date record of label use prior to the restart. This could occur, if prior to the restart, the:
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Label usage information on the active RP was updated when the standby RP was inaccessible.
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Restart occurred before the active RP has the opportunity to update the standby persistent data.
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RP selected to be the active RP was the standby prior to the restart.
If this occurs, it is undetectable and the MPLS Safe Label Reuse feature cannot prevent unsafe label
reuse following such a restart.
reuse following such a restart.
Information About MPLS Safe Label Reuse
You should understand the following information before using the MPLS Safe Label Reuse After Router
Restart feature:
Restart feature:
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Safe Label Reuse After a Router Restart Feature Description
If the MPLS Safe Label Reuse feature is not configured, when a router restarts no record of local labels
in use prior to the restart is available. Such a router might bind local labels to Forwarding Equivalence
Classes (FECs) differently than it did before the restart. If this happens, traffic could be forwarded
incorrectly for a short period of time until neighbor routers remove forwarding information based on
labels learned from the restarting router prior to its restart.
in use prior to the restart is available. Such a router might bind local labels to Forwarding Equivalence
Classes (FECs) differently than it did before the restart. If this happens, traffic could be forwarded
incorrectly for a short period of time until neighbor routers remove forwarding information based on
labels learned from the restarting router prior to its restart.
The MPLS Safe Label Reuse After Router Restart feature, available in Cisco IOS Release 12.0(32)SY
and later releases, prevents a restarting router from using local labels that had been in use prior to the
restart until it is safe to do so.
and later releases, prevents a restarting router from using local labels that had been in use prior to the
restart until it is safe to do so.
With this feature, the router keeps a record of the labels that are in use during normal operation in a
persistent data file located on its NVRAM device, which is found on all Cisco IOS platforms. For
example:
persistent data file located on its NVRAM device, which is found on all Cisco IOS platforms. For
example:
Router# dir nvram: