BFD Overview
Feature Name |
Release Information |
Feature Description |
Multihop Bidirectional Forwarding Detection on IPv4 and IPv6 Non-DefaultVRFs |
Release 7.10.1 |
Introduced in this release on: NCS 5500 fixed port routers; NCS 5700 fixedport routers; NCS 5500 modular routers (NCS 5500 line cards; NCS 5700 line cards [Mode: Compatibility; Native]) (select variants only*) You can now improve the reliability of your network by providing earlynotification of failures. This is made possible due to extension of Multihop Bidirectional Forwarding Detection (BFD) for IPv4 and IPv6 non-default VRFs to process BFD packets encapsulated with MPLS label for a particular VRF. *NCS 5700 line cards in compatibility and native modes support this feature for IPv4 non-default VRFs. Other variants listed here already support this feature for IPv4 non-default VRFs. |
Multihop BFD for IPv4 Non-default VRF |
Release 7.7.1 |
BFD provides fast forwarding path failure detection between two routingdevices that are connected by a network link. BFD Multihop enables you to detect connectivity between routers that span multiple network hops and follow unpredictable paths. Prior to this release, BFD Multihop was supported on default VRFs only. This feature provides you the flexibility to extend BFD Multihop for IPv4 non-defaultVRFs. |
BFD Support for VRRP |
Release 7.5.1 |
This feature is now supported on routers that have the Cisco NC57 line cards installed and operate in native and compatible modes. This feature introduces BFD support over VRRP interfaces. |
IPv4 BFD Multihop over MPLS Core and Segment Routing |
Release 7.5.1 |
Thisfeature is now supported on routers that have the Cisco NC57 line cards that are installed and operate in native and compatible modes. This feature enables you to configure IPv4 Multihop BFD on MPLS LDP and Segment Routing. |
Coexistence of BFD Over Bundle and BFD over Logical Bundle |
Release 7.4.1 |
Thisfeature provides the benefits of both BFD over bundle (BOB) and BFD over logical bundle (BLB). This feature enables you to configure both BOB and BLB over physical bundle interfaces and subinterfaces. BOB functionality allows you to detect failures in physical bundle interfaces. BLB functionality allows you to detect failures in the client protocols configured on the subinterfaces. |
BFD over Logical Bundle |
Release 7.4.1 |
This feature is now supported on routers that have Cisco NC57 line cards installed and operate in compatibility mode. The BLB feature implements and deploys BFD over bundle VLAN interfaces. The advantage of BFD, low-overhead and short-duration detection of path failures between routers, is extended to bundle VLAN interfaces. |
IPv4 and IPv6 Multihop BFD Support |
Release 7.4.1 |
BFD IPv6 Multihop feature enables IPv6 Multihop BFD sessions whereBFD neighbors can be multiple hops away, either physically or logically. It removes the restriction of a single path IPv6 BFD session, where theBFD neighbor is always one hop away, and the BFD Agent in the line card always receives or transmits BFD packets over a local interfaceon the same line card. Thus, the advantage of BFD, low-overhead and short-duration detectionof path failures between (IPv6) routers, is extended to a multihop scenario. Thisfeature is also supported on routers that have Cisco NC57 line cards installed and operate in native and compatibility modes. IPv4 Multihop BFD is a BFD session between two nodes, such as a PEand CE node, or between routers that are several TTL hops away. This feature provides subsecond forwarding failure detection for a destination more than one hop, and up to 255 hops away. Thus, the advantage of BFD, low-overhead, and short-duration detectionof path failures between routers, is extended to a multihop scenario. |
BFD Over BVI |
Release 7.4.1Release 7.3.1Release 7.5.1 |
This feature is now supported on routers that have Cisco NC57 line cards installed and operate in native and compatibility modes. This feature is also supported on routers that have Cisco NCS550x and Cisco NCS55Ax line cards installed and operate in native and compatibility modes. BFD over IRB, using a BVI, is a multipath single-hop session. In a BFD multipath session, BFD can be applied over virtual interfaces or between interfaces that are multihops away. The advantage of BFD, low-overhead and short-duration detection of path failures between routers, is extended to an IRB deployment scenario. BFD can be configured on Bridge group Virtual Interface (BVI). BVI is a virtual interface within the router that acts like a normal routed interface that does not support bridging but represents the bridge group for the bridged physical interfaces. BFD detects the Layer3 fault over the BVI much quicker and inform the same to routing protocols. Starting from Cisco IOS XR Release 7.1.1, BFD over BVI is supported on fixed NCS5500 platforms. |
BFD for BoB with IPv4 Unnumbered |
Release 7.3.1 |
This feature is now supported on routers that have Cisco NC57 line cards installed and operate in the native mode. |
BFDv6 - HW Offload and IPv6 BFD/BoB (Bundle over Bundle) |
Release 6.6.1 |
The Bidirectional Forwarding detection (BFD) Hardware Offload feature enables the offload of a BFD session in an IPv6 network. With this feature, each bundle member link with IPv6 address runs its own BFD session This feature improves scale and reduces the overall network convergence time by sending rapid failure detection packets to the routing protocols for recalculating the routing table. |
Bidirectional Forwarding Detection (BFD) provides low-overhead, short-duration detection of failures in the path between adjacent routers. BFD allows a single mechanism to be used for failure detection over any media and at any protocol layer, with a wide range of detection times and overhead. The fast detection of failures provides immediate reaction to failure in the event of a failed link or neighbor.
![]() Tip |
You can programmatically configure BFD and retrieve operational data using |
Features Unsupported
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BFD echo mode and encryption are not supported.
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BFD over MPLS tunnel interfaces is not supported.
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Dampening extensions for BFD are not supported.
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BFD down dampening is not supported.
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BFD IPv6 Dampening is not supported.
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SNMP traps are not supported for multipath BFD sessions.
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BFD Over GRE is not supported.
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BFD over PWHE is not supported.
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Seamless BFD is not supported.
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BFD over Satellite interface is not supported.
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BFD Authentication is not supported.
Supported Functionalities
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BFD hardware offload is supported for both IPv4 and IPv6.
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Starting from IOS XR Release 6.3.2, BFD dampening for IPv4 is supported.
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Starting from IOS XR Release 6.3.2, BFD multihop over an IP core is supported.
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BFD over Bundle (BoB) over IPv6 is not supported with dyamically configured link-local address. It must be statically configured.
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Egress IPv4 ACLs block all traffic, including router-generated traffic for the following routers and line cards:
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NC57-24DD
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NC57-18DD-SE
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NC57-36H-SE
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NC57-36H6D-S
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NC57-MOD-S
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NCS-57B1-6D24-SYS
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NCS-57B1-5DSE-SYS
For all other routers and line cards, egress IPv4 ACLs do not block certain router-generated traffic, such as ICMP messages.
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Feature Limitations
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Egress ACL with drop rule for src-ip equal to 0.0.0.0 will drop BFD-V4 Tx packets on that interface. This is because, BFD-V4 packets generated by OAMP will have src.ip 0.0.0.0 due to its limitation. And the actual source IP value is filled in ETPP block in pipeline before sending the packet. Since egress ACL is applied before ETPP, the BFD packets are dropped.
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BFD over bundle feature is supported only in IETF mode.
BFD Timers
![]() Note |
If the timer is configured below the minimum timer supported, some undesirable behavior can be seen in BFD. customers some time will configure 3 msec as timer and will miss the minimum timer of 4 msec. |
![]() Note |
BFD HW (OAMP) supports 8 timer profiles, each profile is assigned to unique bfd minimum-interval value. Out of these, two profiles are reserved and another profile is reserved if BFD over Bundle (BoB) is configured. So, 6 profiles are available without BoB config and 5 profiles with BoB. |
Type of BFD Session |
Minimum Timer Supported |
Minimum Multipliers Value |
Supported Minimum-Interval Value (Up to 6 Unique Timers Profiles) |
---|---|---|---|
Single Hop |
4ms |
3 |
Any |
BFD over Bundle Members (BoB) |
4ms |
3 |
Any |
BFD over Logical bundle (BLB) |
100ms (starting Release 24.3.1) 300ms (prior to Release 24.3.1) |
3 |
Any |
BGP Multi Hop |
50ms |
3 |
Any |
BFD Over BVI |
50ms |
3 |
Any |
Type of BFD Session |
Minimum Timer Supported |
Minimum Multipliers Value |
Supported Timer Profile (Up to 6 unique timer profiles) |
Maximum Scale depending on Minimum Interval |
---|---|---|---|---|
Single Hop |
4ms |
3 |
Any |
150 (with 8ms and above, all 256 sessions are configurable) |
BFD over Bundle Members (BoB) |
4ms |
3 |
Any |
150ms (with 8ms and above, all 256 sessions are configurable) |
BFD over Logical bundle (BLB) |
100ms (starting Release 24.3.1) 300ms (prior to Release 24.3.1) |
3 |
Any |
256 |
BGP Multi Hop |
50ms |
3 |
Any |
256 |
BFD Over BVI |
50ms |
3 |
Any |
250 or Max MP scale- whichever is lower |