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This module contains information for enabling the Bidirectional Forwarding Detection (BFD) detection protocol on Protocol Independent Multicast (PIM) interfaces in your IP v4 and IPv6 network. Enabling PIM BFD enables PIM to use BFD's quicker adjacent system failure detection and avoid the slower query-interval in its own detection mechanisms.
This feature is not supported for Multicast VPN (MVPN).
This feature is supported only on interfaces on which both PIM and BFD are supported.
Information About BFD Support for Multicast (PIM)
Bidirectional Forwarding Detection (BFD) is a detection protocol designed to provide fast forwarding path failure detection times for all media types, encapsulations, topologies, and routing protocols and independent of the higher layer protocols. In addition to fast forwarding path failure detection, BFD provides a consistent failure detection method for network administrators. Because the network administrator can use BFD to detect forwarding path failures at a uniform rate, rather than the variable rates for different routing protocol hello mechanisms, network profiling and planning is easier and reconvergence time is consistent and predictable.
Protocol Independent Multicast (PIM) uses a hello mechanism for discovering new neighbors and for detecting failures between adjacent nodes. The minimum failure detection time in PIM is 3 times the PIM Query-Interval. To enable faster failure detection, the rate at which a PIM Hello message is transmitted on an interface is configurable. However, lower intervals increase the load on the protocol and can increase CPU and memory utilization and cause a system-wide negative impact on performance. Lower intervals can also cause PIM neighbors to expire frequently as the neighbor expiry can occur before the hello messages received from those neighbors are processed.
The BFD Support for Multicast (PIM) feature, also known as PIM BFD, registers PIM as a client of BFD. PIM can then utilize BFD to initiate a session with an adjacent PIM node to support BFD's fast adjacency failure detection in the protocol layer. PIM registers just once for both PIM and IPv6 PIM.
At PIMs request (as a BFD client), BFD establishes and maintains a session with an adjacent node for maintaining liveness and detecting forwarding path failure to the adjacent node. PIM hellos will continue to be exchanged between the neighbors even after BFD establishes and maintains a BFD session with the neighbor. The behavior of the PIM hello mechanism is not altered due to the introduction of this feature.
Although PIM depends on the Interior Gateway Protocol (IGP) and BFD is supported in IGP, PIM BFD is independent of IGP's BFD.
How to Configure BFD Support for Multicast (PIM)
For IPv4 networks, IP multicast must be enabled and Protocol Independent Multicast (PIM)must be configured on the interface. For information, see the “Configuring Basic IP Multicast in IPv4 Networks” module of the IP Multicast: PIM Configuration Guide.
For IPv6 networks, IPv6 multicast must be enabled and Protocol Independent Multicast (PIM) must be configured on the interface. For information, see the IP Multicast: PIM Configuration Guide.
| Command or Action | Purpose | |
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Step 1 |
enable Example: |
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Step 2 |
configure terminal Example: |
Enters global configuration mode. |
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Step 3 |
interfacetype number Example: |
Enters interface configuration mode for the specified interface. |
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Step 4 |
bfd interval milliseconds min_rx milliseconds multiplier interval-multiplier Example: |
Enables BFD on the interface. |
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Step 5 |
Use one of the following:
Example: |
Enables PIM BFD on the interface. |
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Step 6 |
Repeat the preceding steps for each interface to be enabled for BFD PIM. |
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Step 7 |
end Example: |
Exits to privileged EXEC mode . |
Configuration Examples for BFD Support for Multicast (PIM)
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Related Topic |
Document Title |
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Cisco IOS commands |
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IP multicast commands |
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Bidirectional Forwarding Detection (BFD) detection protocol |
IP Routing BFD Configuration Guide |
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Protocol Independent Multicast (PIM) in an IPv4 network |
“Configuring Basic IP Multicast in IPv4 Networks” module of the IP Multicast: PIM Configuration Guide |
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PIM in an IPv6 network |
IP Multicast: PIM Configuration Guide |
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Description |
Link |
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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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