Cisco IOS XR Interface and Hardware Component Configuration Guide, Release 3.2
Configuring Bidirectional Forwarding Detection on Cisco IOS XR Software
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Table Of Contents

Configuring Bidirectional Forwarding Detection on Cisco IOS XR Software

Contents

Prerequisites for Implementing BFD

Information About BFD

BFD Packet Formats

Configuring BFD

Prerequisites

Restrictions

Configuration Examples for Configuring Bidirectional Forwarding Detection on Cisco IOS XR

Bidirectional Forwarding Detection: Example

Where to Go Next

Additional References

Related Documents

Standards

\RFCs

Technical Assistance


Configuring Bidirectional Forwarding Detection on Cisco IOS XR Software

Bidirectional forwarding detection (BFD) provides low-overhead, short-duration detection of failures in the path between adjacent forwarding engines. 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.

Feature History for Configuring Bidirectional Forwarding Detection on Cisco IOS XR Software

Release
Modification

Release 3.2

This feature was introduced on the Cisco CRS-1 router.


Contents

•Prerequisites for Implementing BFD

•Information About BFD

•Configuration Examples for Configuring Bidirectional Forwarding Detection on Cisco IOS XR

•Where to Go Next

•Additional References

Prerequisites for Implementing BFD

The following are required to implement BFD:

•You must be in a user group associated with a task group that includes the proper task IDs for the BFD commands. Task IDs for commands are listed in the Cisco IOS XR Task ID Reference Guide.

For detailed information about user groups and task IDs, refer to the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

•A Cisco CRS-1 router that runs Cisco IOS XR software.

•If enabling BFD on Multiprotocol Label Switching (MPLS), an installed composite PIE file including the MPLS package, or a composite-package image is required. For Border Gateway Protocol (BGP), Intermediate System-to-Intermediate System (IS-IS), and Open Shortest Path First (OSPF), an installed Cisco IOS XR IP Unicast Routing Core Bundle image is required.

•IGP is activated on the router if you are using IS-IS or OSPF.

Information About BFD

Cisco IOS XR supports BFD for the verification of IPv4 single-hop connectivity. Cisco IOS XR supports both Asynchronous mode and Echo mode. Echo mode is initiated only after a session is established using BFD control packets.

BFD is a fixed-length hello protocol, where each end of a connection transmits packets periodically over a forwarding path. Cisco IOS XR supports BFD adaptive detection times.

BFD can be used with the following protocols:

•BGP

•IS-IS

•OSPF

•MPLS traffic-engineering (MPLS-TE)

Note BFD is supported on IPv4 directly connected external BGP peers.

BFD is supported for connections over the following interface types:

•Packet-over-SONET (PoS)

•gigabit Ethernet (GigE)

•ten gigabit Ethernet (TenGigE)

•virtual LAN (VLAN)

BFD Packet Formats

BFD payload control packets are encapsulated in UDP packets, using destination port 3784 and source port 49152. Even on shared media, like Ethernet, BFD control packets are always sent as unicast packets to the BFD peer.

Echo packets are encapsulated in UDP packets, as well, using destination port 3785 and source port 3785.

Configuring BFD

The following procedure describes how to configure BFD for BGP. The steps in the procedure are common to all BFD-supported protocols (IS-IS, OSPF, and MPLS-TE), only the command mode differs.

Prerequisites

To enable BFD for a neighbor, the neighbor router must support BFD.

Restrictions

The following interface types are supported:

•PoS

•GigE

•TenGigE

•VLAN

BFD is supported on IPv4 directly connected external BGP peers.

Note Unnumbered interfaces are not supported.

SUMMARY STEPS

1. configure

2. router bgp autonomous-system-number

3. bfd minimum-interval milliseconds

4. bfd multiplier multiplier

5. neighbor ip-address

6. remote-as autonomous-system-number

7. bfd fast-detect

8. end
or
commit

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step 2 

router bgp autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode, allowing you to configure the BGP routing process.

Note To configure BFD for IS-IS, OSPF, or MPLS-TE, enter the corresponding configuration mode. For example, for MPLS-TE, enter MPLS-TE configuration mode.

Step 3 

bfd minimum-interval milliseconds

Example:

RP/0/RP0/CPU0:router(config-bgp)# bfd minimum-interval 6500

Sets the BFD minimum interval. Range is 15-30000 milliseconds.

This example sets the BFD minimum interval to 6500 milliseconds.

Step 4 

bfd multiplier multiplier

Example:

RP/0/RP0/CPU0:router(config-bgp)# bfd multiplier 7

Sets the BFD multiplier.

This example sets the BFD multiplier to 7.

Step 5 

neighbor ip-address

Example:

RP/0/RP0/CPU0:router(config-bgp)# neighbor 172.168.40.24

Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address as a BGP peer.

This example configures the IP address 172.168.40.24 as a BGP peer.

Step 6 

remote-as autonomous-system-number

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)# remote-as 2002

Creates a neighbor and assigns it a remote autonomous system.

This example configures the remote autonomous system to be 2002.

Step 7 

bfd fast-detect

Example:

RP/0/RP0/CPU0:router(config-bgp-nbr)# bfd fast-detect

Enables BFD between the local networking devices and the neighbor whose IP address you configured to be a BGP peer in Step 5.

In the example in Step 5, the IP address 172.168.40.24 was set up as the BGP peer. In this example, BFD is enabled between the local networking devices and the neighbor 172.168.40.24.

Step 8 

end

or

commit

Example:

RP/0/RP0/CPU0:router (config-bgp-nbr)# end

or

RP/0/RP0/CPU0:router(config-bgp-nbr)# commit

Saves configuration changes.

•When you issue the end command, the system prompts you to commit changes:
Uncommitted changes found. Commit them?

–Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.

–Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.

–Entering cancel leaves the user in the same command mode without committing the configuration changes.

•Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.

Configuration Examples for Configuring Bidirectional Forwarding Detection on Cisco IOS XR

This section provides the following configuration example:

•Bidirectional Forwarding Detection: Example

Bidirectional Forwarding Detection: Example

The following example shows how to configure BFD between autonomous system 65000 and neighbor 192.168.70.24. 

RP/0/RP0/CPU0:router(config)# router bgp 65000

RP/0/RP0/CPU0:router(config-bgp)# bfd multiplier 2

RP/0/RP0/CPU0:router(config-bgp)# bfd minimum-interval 20

RP/0/RP0/CPU0:router(config-bgp)# neighbor 192.168.70.24

RP/0/RP0/CPU0:router(config-bgp-nbr)# remote-as 2

RP/0/RP0/CPU0:router(config-bgp-nbr)# bfd fast-detect

Where to Go Next

BFD is supported over multiple platforms; refer to the related command reference document for more detailed information about these commands.

•BGP Commands on Cisco IOS XR Software

•IS-IS Commands on Cisco IOS XR Software

•OSPF Commands on Cisco IOS XR Software

•MPLS Traffic Engineering Commands on Cisco IOS XR Software

Additional References

The following sections provide references related to implementing BFD for Cisco IOS XR software.

Related Documents

Related Topic
Document Title

BFD commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples

Cisco IOS XR Interface and Hardware Command Reference, Release 3.2


Standards

Standards
Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

—


\RFCs

RFCs
Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

—


Technical Assistance

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Link

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