Setting Up Bfd Multihop; Bfd Over Mpls Traffic Engineering Lsps; Echo Timer Configuration For Bfd On Bundle Interfaces - Cisco ASR 9000 Series Routing Configuration Manual

Implementing BFD

Setting up BFD Multihop

A BFD multihop 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. For BFD Multihop, IPv4 addresses in
both global routing table and in a VRF is supported.

BFD over MPLS Traffic Engineering LSPs

Bidirectional Forwarding Detection ( BFD) over MPLS Traffic Engineering Label Switched Paths (LSPs)
feature in Cisco IOS XR Software detects MPLS Label Switched Path LSP data plane failures. Since the
control plane processing required for BFD control packets is relatively smaller than the processing required
for LSP Ping messages, BFD can be deployed for faster detection of data plane failure for a large number of
LSPs.
The BFD over MPLS TE LSPs implementation in Cisco IOS XR Software is based on RFC 5884: Bidirectional
Forwarding Detection (BFD) for MPLS Label Switched Paths (LSPs). LSP Ping is an existing mechanism
for detecting MPLS data plane failures and for verifying the MPLS LSP data plane against the control plane.
BFD can be used for for detecting MPLS data plane failures, but not for verifying the MPLS LSP data plane
against the control plane. A combination of LSP Ping and BFD provides faster data plane failure detection
on a large number of LSPs.
The BFD over MPLS TE LSPs is used for networks that have deployed MPLS as the multi service transport
and that use BFD as fast failure detection mechanism to enhance network reliability and up time by using
BFD as fast failure detection traffic black holing.
BFD over MPLS TE LSPs support:
• BFD async mode (BFD echo mode is not supported)
• IPv4 only, since MPLS core is IPv4
• BFD packets will carry IP DSCP 6 (Internet Control)
• Use of BFD for TE tunnel bring up, re-optimization, and path protection (Standby and FRR)
• Fastest detection time (100 ms x 3 = 300 ms)
• Optional Periodic LSP ping verification after BFD session is up
• Dampening to hold-down BFD failed path-option
• There are two ways in which the BFD packets from tail-end to head-end will be used:

Echo Timer configuration for BFD on Bundle Interfaces

The echo timer configuration allows you to specify the minimum interval for echo packets on IPv4 BFD
sessions on bundle member links. You can set the echo timer value globally using the bfd echo ipv4
bundle-per-member minimum-interval command. Use the bfd address-family ipv4 echo minimum-interval
to locally set the minimum interval value for the bundle ethernet interface.
◦ BFD packets from tail-end to head-end will be IP routed (IPv4 Multihop - port# 4784)
◦ BFD packets from tail-end to head-end will be Label Switched (port# 3784) if MPLS LDP is
available in Core with label path from tail-end to head-end.
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.3.x
BFD over MPLS Traffic Engineering LSPs
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