Bfd Multipath Sessions; Bfd For Multihop Paths - Cisco ASR 9000 Series Routing Configuration Manual

BFD Multipath Sessions

• Another threshold is configurable on the bundle and is used by the bundle manager to determine the
• The BFD server responds to information from the bundle manager about state changes for the bundle
BFD Multipath Sessions
BFD can be applied over virtual interfaces such as GRE tunnel interfaces, PWHE interfaces, or between
interfaces that are multihops away as described in the
sessions are referred to BFD Multipath sessions.
As long as one path to the destination is active, these events may or may not cause the BFD Multipath session
to fail as it depends on the interval negotiated versus the convergence time taken to update forwarding plane:
• Failure of a path
• Online insertion or removal (OIR) of a line card which hosts one or more paths
• Removal of a link (by configuration) which constitutes a path
• Shutdown of a link which constitutes a path
You must configure bfd mutlipath include location location-id command to enable at least one line card for
the underlying mechanism that can be used to send and receive packets for the multipath sessions.
If a BFD Multipath session is hosted on a line card that is being removed from the bfd multipath include
configuration, online removed, or brought to maintenance mode, then BFD attempts to migrate all BFD
Multipath sessions hosted on that line card to another one. In that case, static routes are removed from RIB
and then the BFD session is established again and included to RIB.
For more information on PW headend and its configuration, see Implementing Virtual Private LAN Services
module in the Cisco ASR 9000 Series Aggregation Services Router L2VPN and Ethernet Services Configuration
Guide. For more information on GRE, see Implementing MPLS Layer 2 VPNs module in Cisco ASR 9000
Series Aggregation Services Router L2VPN and Ethernet Services Configuration Guide

BFD for MultiHop Paths

BFD multihop (BFD-MH) is a BFD session between two addresses that are not on the same subnet. An
example of BFD-MH is a BFD session between PE and CE loopback addresses or BFD sessions between
routers that are several TTL hops away. The applications that support BFD multihop are external and internal
BGP. BFD multihop supports BFD on arbitrary paths, which can span multiple network hops.
The BFD Multihop feature provides sub-second forwarding failure detection for a destination more than one
hop, and up to 255 hops, away. The bfd multihop ttl-drop-threshold command can be used to drop BFD
packets coming from neighbors exceeding a certain number of hops. BFD multihop is supported on all currently
supported media-type for BFD singlehop.
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minimum amount of active bandwidth to be available before the bundle goes to DOWN state. This is
configured using the bundle minimum-active bandwidth command.
interface and notifies applications on that interface while also sending system messages and MIB traps.
BFD for MultiHop Paths section. These types of BFD
Implementing BFD