Cisco Cisco IOS Software Release 12.0(22)S
MPLS Traffic Engineering— Overload Avoidance Support for IS-IS
Feature Overview
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Cisco IOS Release: Multiple releases (see the Feature History table)
Feature Overview
Occasionally you may want a router in an IS-IS network to not carry traffic. For example:
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A test router in a lab that is connected to a production network.
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A router configured as an link-state packet (LSP) flooding server (on an nonbroadcast multiaccess
(NBMA) network, for example) in combination with the mesh-group feature.
(NBMA) network, for example) in combination with the mesh-group feature.
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A router that is aggregating virtual circuits (VC), being used only for network management.
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A router that is experiencing a memory shortage, making its routing table inaccurate or incomplete.
This new feature is implemented through a single command, mpls traffic-eng path-selection overload
allow. For the reader’s convenience, we have also included information about an older command,
set-overload-bit (which had already been fully documented in the Cisco IOS IP Configuration Guide
and Command Reference), because the new command’s function is so closely tied to that older command
allow. For the reader’s convenience, we have also included information about an older command,
set-overload-bit (which had already been fully documented in the Cisco IOS IP Configuration Guide
and Command Reference), because the new command’s function is so closely tied to that older command
To isolate any such router, you turn on the set-overload-bit command (described in detail on page 5).
Doing so will allow other routers to ignore this router in their SPF calculations. No paths through this
router will be seen by other routers in the IS-IS area. (Nevertheless, IP and Connectionless Network
Service (CLNS) prefixes directly connected to this router still will be reachable).
Doing so will allow other routers to ignore this router in their SPF calculations. No paths through this
router will be seen by other routers in the IS-IS area. (Nevertheless, IP and Connectionless Network
Service (CLNS) prefixes directly connected to this router still will be reachable).
Now, you can selectively override the overload bit with respect to Multiprotocol Label Switching
(MPLS) LSPs by using a new command: mpls traffic-eng path-selection overload allow. This
command enables the operator to include an overloaded node in CSPF.
(MPLS) LSPs by using a new command: mpls traffic-eng path-selection overload allow. This
command enables the operator to include an overloaded node in CSPF.
Prerequisites
Your network must support the following Cisco IOS features in order for this command to have any
effect:
effect:
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MPLS
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IS-IS
Command Reference
This section documents modified commands only.
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