IP Routing: BFD Configuration Guide, Cisco IOS XE Release 3S (Cisco ASR 1000)
IS-IS Client for BFD C-Bit Support
IS-IS Client for BFD C-Bit Support
Last Updated: July 17, 2012
The Bidirectional Forwarding Detection (BFD) protocol provides short-duration detection of failures in the path between adjacent forwarding engines while maintaining low networking overheads. The BFD IS-IS Client Support feature enables Intermediate System-to-Intermediate System (IS-IS) to use Bidirectional Forwarding Detection (BFD) support, which improves IS-IS convergence as BFD detection and failure times are faster than IS-IS convergence times in most network topologies. The IS-IS Client for BFD C-Bit Support feature enables the network to identify whether a BFD session failure is genuine or is the result of a control plane failure due to a router restart. When planning a router restart, you should configure this feature on all neighboring routers.
Finding Feature Information
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Prerequisites for IS-IS Client for BFD C-Bit Support
Information About IS-IS Client for BFD C-Bit Support
IS-IS Restarts and BFD Sessions
The IS-IS Client for BFD C-Bit Support feature provides BFD with a way to signal to its peers whether the BFD implementation shares the same status as the control plane. When a neighboring router's control plane restarts, a BFD session failure may occur, which does not actually represent a true forwarding failure. If this happens, you do not want the neighbors of the restarting router to react to the BFD session failure.
IS-IS does not have protocol extensions that allow it to signal in advance that it will be restarting. This means that the system cannot distinguish between a real forwarding failure and a restart. The IS-IS Client for BFD C-Bit Support feature allows you to configure the device to ignore control-plane related BFD session failures. We recommend that you configure this feature on the neighbors of a restarting device just prior to the planned restart of that device and that you remove the configuration after the restart has been completed.
The table below shows how the control plane independent failure status received from BFD on a session down event impacts IS-IS handling of that event.
How to Configure IS-IS Client for BFD C-Bit Support
Configuring IS-IS Client for BFD C-Bit Support
2. configure terminal
3. router isis
4. bfd check-control-plane-failure
Configuration Examples for IS-IS Client for BFD C-Bit Support
Example: Configuring IS-IS Client for BFD C-Bit Support
Standards and RFCs
Feature Information for IS-IS Client for BFD C-Bit Support
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
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