Configuring Multihop Bidirectional Forwarding Detection

Cisco ASR 901 supports Bidirectional Forwarding Detection(BFD) on arbitrary paths, which can span multiple network hops. The multihop BFD feature provides subsecond forwarding failure detection for a destination with more than one hop and up to 255 hops. A multihop BFD session is set up between a unique source-destination address pair provided by the client. A session can be set up between two endpoints that have IP connectivity.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information for LLDP.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn . An account on Cisco.com is not required.

Restrictions for Multihop BFD

The following are the restrictions for multihop BFD:

  • BFD does not support echo mode. You can configure sessions for minimum timer interval.
  • The minimum guaranteed timer depends on the topology, scale, number of hops, and control plane processing. All the packets must reach the control plane since echo mode is not supported.
  • Supports IPv4 deployments only.
  • Authentication for multihop BFD is not enabled on Cisco ASR901 routers.

Information About Multihop BFD

Overview of Multihop BFD

Cisco ASR 901 supports BFD on arbitrary paths, which can span multiple network hops. You must configure the bfd-template and bfd map commands to create a multihop template and associate it with one ore more maps of destinations and associated timers. You can enable authentication and configure a key chain for multihop BFD sessions.

How to Configure Multihop BFD

This section contains the following procedures:

Configuring Multihop BFD Template

Complete the following steps to create a multihop BFD template and configure BFD interval timers, authentication, and key chain:

Procedure

  Command or Action Purpose

Step 1

enable

Example:


Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:


Router# configure terminal

Enters global configuration mode.

Step 3

bfd-template multi-hop template-name

Example:


Router(config)# bfd-template 
multi-hop mh-template1

Creates a BFD multihop BFD template and enters BFD configuration mode.

Step 4

interval min-tx milliseconds min-rx milliseconds multiplier multiplier-value

Example:


Router(bfd-config)# interval 
min-tx 120 min-rx 100 multiplier 3

Configures the transmit and receive intervals between BFD packets, and specifies the number of consecutive BFD control packets that must be missed before BFD declares that a peer is unavailable.

Step 5

authentication authentication-type keychain keychain-name

Example:


Router(bfd-config)# authentication keyed-sha-1 
keychain bfd-multihop

Configures authentication for the multihop template and the authentication type.

Step 6

end

Example:


Router(bfd-config)# end

Returns the router to privileged EXEC mode.

Configuring a Multihop BFD Map

After configuring the interval timers and authentication in a template, you must configure a map to associate the template with unique source-destination address pairs for multihop BFD sessions.

Procedure

  Command or Action Purpose

Step 1

enable

Example:


Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:


Router# configure terminal

Enters global configuration mode.

Step 3

bfd mapipv4 vrf vrf-name destination-address/length source-address/length template-name

Example:


Router(config)# bfd-template multi-hop mh-template1

Configures a BFD map and associates it with the template.

Step 4

end

Example:


Router(config)# end

Returns the router to privileged EXEC mode.

Configuration Examples for Multihop BFD

This section provides the configuration example for multihop BFD.

Example : Configuring Multihop BFD

The following example shows how to configure BFD in a BGP network. In the following example, the simple BGP network consists of Router A and Router B. Fast Ethernet interface 0/1 on Router A is connected to the same network as Fast Ethernet interface 6/0 in Router B.

Configuration for Router A 


!
interface Fast Ethernet 0/1
ip address 172.16.10.1 255.255.255.0
bfd interval 50 min_rx 50 multiplier 3
!
interface Fast Ethernet 3/0.1
ip address 172.17.0.1 255.255.255.0
!
!
router bgp 40000
bgp log-neighbor-changes
neighbor 172.16.10.2 remote-as 45000
neighbor 172.16.10.2 fall-over bfd
!
address-family ipv4
neighbor 172.16.10.2 activate
no auto-summary
no synchronization
network 172.18.0.0 mask 255.255.255.0
exit-address-family
!

Configuration for Router B 


!
interface Fast Ethernet 6/0
ip address 172.16.10.2 255.255.255.0
bfd interval 50 min_rx 50 multiplier 3
!
interface Fast Ethernet 6/1
ip address 172.18.0.1 255.255.255.0
!
router bgp 45000
bgp log-neighbor-changes
neighbor 172.16.10.1 remote-as 40000
neighbor 172.16.10.1 fall-over bfd
!

address-family ipv4
neighbor 172.16.10.1 activate
no auto-summary
no synchronization
network 172.17.0.0 mask 255.255.255.0
exit-address-family
!

Where to Go Next

For additional information on configuring Multihop BFD, see the documentation listed in the Additional References section.

Additional References

The following sections provide references related to LLDP feature.

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

Cisco ASR 901 Command Reference

Cisco ASR 901 Series Aggregation Services Router Command Reference

Cisco IOS Interface and Hardware Component Commands

Cisco IOS Interface and Hardware Component Command Reference

Standards

Standard

Title

None

—

MIBs

MIB

MIBs Link

None

To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/c/en/us/td/docs/wireless/asr_901/mib/reference/asr_mib.html

RFCs

RFC

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

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

http://www.cisco.com/cisco/web/support/index.html

Feature Information for Multihop BFD

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn . An account on Cisco.com is not required.

Table 1 lists the release history for this feature and provides links to specific configuration information.


Note
Table 1 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.
Table 1. Feature Information for Multihop BFD

Feature Name

Releases

Feature Information

Multihop BFD

15.2(2)SNG

See the following links for more information about this feature: