:abbr:`BFD (Bidirectional Forwarding Detection)` stands for Bidirectional Forwarding Detection and it is described and extended by the following RFCs:
Currently, there are two implementations of the BFD commands in FRR:
- :abbr:`PTM (Prescriptive Topology Manager)`: an external daemon which implements BFD;
bfdd: a BFD implementation that is able to talk with remote peers;
This document will focus on the later implementation: bfdd.
bfdd default configuration file is :file:`bfdd.conf`. bfdd searches the current directory first then |INSTALL_PREFIX_ETC|/bfdd.conf. All of bfdd's command must be configured in :file:`bfdd.conf`.
bfdd specific invocation options are described below. Common options may also be specified (:ref:`common-invocation-options`).
.. program:: bfdd
.. option:: --bfdctl <unix-socket>
Set the BFD daemon control socket location. If using a non-default
socket location::
/usr/lib/frr/bfdd --bfdctl /tmp/bfdd.sock
The default UNIX socket location is:
#define BFDD_CONTROL_SOCKET "|INSTALL_PREFIX_STATE|/bfdd.sock"
This option overrides the location addition that the -N option provides
to the bfdd.sock
.. option:: --dplaneaddr <type>:<address>[<:port>]
Configure the distributed BFD data plane listening socket bind address.
One would expect the data plane to run in the same machine as FRR, so
the suggested configuration would be:
--dplaneaddr unix:/var/run/frr/bfdd_dplane.sock
Or using IPv4:
--dplaneaddr ipv4:127.0.0.1
Or using IPv6:
--dplaneaddr ipv6:[::1]
It is also possible to specify a port (for IPv4/IPv6 only):
--dplaneaddr ipv6:[::1]:50701
(if ommited the default port is ``50700``).
It is also possible to operate in client mode (instead of listening for
connections). To connect to a data plane server append the letter 'c' to
the protocol, example:
--dplaneaddr ipv4c:127.0.0.1
Note
When using UNIX sockets don't forget to check the file permissions before attempting to use it.
.. clicmd:: bfd Opens the BFD daemon configuration node.
.. clicmd:: peer <A.B.C.D|X:X::X:X> [{multihop|local-address <A.B.C.D|X:X::X:X>|interface IFNAME|vrf NAME}]
Creates and configures a new BFD peer to listen and talk to.
`multihop` tells the BFD daemon that we should expect packets with
TTL less than 254 (because it will take more than one hop) and to
listen on the multihop port (4784). When using multi-hop mode
`echo-mode` will not work (see :rfc:`5883` section 3).
`local-address` provides a local address that we should bind our
peer listener to and the address we should use to send the packets.
This option is mandatory for IPv6.
`interface` selects which interface we should use.
`vrf` selects which domain we want to use.
.. clicmd:: profile WORD Creates a peer profile that can be configured in multiple peers. Deleting the profile will cause all peers using it to reset to the default values.
.. clicmd:: show bfd [vrf NAME] peers [json]
Show all configured BFD peers information and current status.
.. clicmd:: show bfd [vrf NAME] peer <WORD|<A.B.C.D|X:X::X:X> [{multihop|local-address <A.B.C.D|X:X::X:X>|interface IFNAME}]> [json]
Show status for a specific BFD peer.
.. clicmd:: show bfd [vrf NAME] peers brief [json]
Show all configured BFD peers information and current status in brief.
.. clicmd:: show bfd distributed Show the BFD data plane (distributed BFD) statistics.
BFD peers and profiles share the same BFD session configuration commands.
.. clicmd:: detect-multiplier (2-255) Configures the detection multiplier to determine packet loss. The remote transmission interval will be multiplied by this value to determine the connection loss detection timer. The default value is 3. Example: when the local system has `detect-multiplier 3` and the remote system has `transmission interval 300`, the local system will detect failures only after 900 milliseconds without receiving packets.
.. clicmd:: receive-interval (10-60000) Configures the minimum interval that this system is capable of receiving control packets. The default value is 300 milliseconds.
.. clicmd:: transmit-interval (10-60000) The minimum transmission interval (less jitter) that this system wants to use to send BFD control packets. Defaults to 300ms.
.. clicmd:: echo receive-interval <disabled|(10-60000)> Configures the minimum interval that this system is capable of receiving echo packets. Disabled means that this system doesn't want to receive echo packets. The default value is 50 milliseconds.
.. clicmd:: echo transmit-interval (10-60000) The minimum transmission interval (less jitter) that this system wants to use to send BFD echo packets. Defaults to 50ms.
.. clicmd:: echo-mode Enables or disables the echo transmission mode. This mode is disabled by default. If you are not using distributed BFD then echo mode works only when the peer is also FRR. It is recommended that the transmission interval of control packets to be increased after enabling echo-mode to reduce bandwidth usage. For example: `transmit-interval 2000`. Echo mode is not supported on multi-hop setups (see :rfc:`5883` section 3).
.. clicmd:: shutdown Enables or disables the peer. When the peer is disabled an 'administrative down' message is sent to the remote peer.
.. clicmd:: passive-mode Mark session as passive: a passive session will not attempt to start the connection and will wait for control packets from peer before it begins replying. This feature is useful when you have a router that acts as the central node of a star network and you want to avoid sending BFD control packets you don't need to. The default is active-mode (or ``no passive-mode``).
.. clicmd:: minimum-ttl (1-254) For multi hop sessions only: configure the minimum expected TTL for an incoming BFD control packet. This feature serves the purpose of thightening the packet validation requirements to avoid receiving BFD control packets from other sessions. The default value is 254 (which means we only expect one hop between this system and the peer).
.. clicmd:: label WORD Labels a peer with the provided word. This word can be referenced later on other daemons to refer to a specific peer.
.. clicmd:: profile BFDPROF
Configure peer to use the profile configurations.
Notes:
- Profile configurations can be overridden on a peer basis by specifying
non-default parameters in peer configuration node.
- Non existing profiles can be configured and they will only be applied
once they start to exist.
- If the profile gets updated the new configuration will be applied to all
peers with the profile without interruptions.
The following commands are available inside the BGP configuration node.
.. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> bfd Listen for BFD events registered on the same target as this BGP neighbor. When BFD peer goes down it immediately asks BGP to shutdown the connection with its neighbor and, when it goes back up, notify BGP to try to connect to it.
.. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> bfd check-control-plane-failure Allow to write CBIT independence in BFD outgoing packets. Also allow to read both C-BIT value of BFD and lookup BGP peer status. This command is useful when a BFD down event is caught, while the BGP peer requested that local BGP keeps the remote BGP entries as staled if such issue is detected. This is the case when graceful restart is enabled, and it is wished to ignore the BD event while waiting for the remote router to restart. Disabling this disables presence of CBIT independence in BFD outgoing packets and pays attention to BFD down notifications. This is the default.
.. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> bfd profile BFDPROF Same as command ``neighbor <A.B.C.D|X:X::X:X|WORD> bfd``, but applies the BFD profile to the sessions it creates or that already exist.
The following commands are available inside the interface configuration node.
.. clicmd:: isis bfd Listen for BFD events on peers created on the interface. Every time a new neighbor is found a BFD peer is created to monitor the link status for fast convergence. Note that there will be just one BFD session per interface. In case both IPv4 and IPv6 support are configured then just a IPv6 based session is created.
.. clicmd:: isis bfd profile BFDPROF Use a BFD profile BFDPROF as provided in the BFD configuration.
The following commands are available inside the interface configuration node.
.. clicmd:: ip ospf bfd Listen for BFD events on peers created on the interface. Every time a new neighbor is found a BFD peer is created to monitor the link status for fast convergence.
.. clicmd:: ip ospf bfd profile BFDPROF Same as command ``ip ospf bfd``, but applies the BFD profile to the sessions it creates or that already exist.
The following commands are available inside the interface configuration node.
.. clicmd:: ipv6 ospf6 bfd [profile BFDPROF] Listen for BFD events on peers created on the interface. Every time a new neighbor is found a BFD peer is created to monitor the link status for fast convergence. Optionally uses the BFD profile ``BFDPROF`` in the created sessions under that interface.
The following commands are available inside the interface configuration node.
.. clicmd:: ip pim bfd [profile BFDPROF] Listen for BFD events on peers created on the interface. Every time a new neighbor is found a BFD peer is created to monitor the link status for fast convergence. Optionally uses the BFD profile ``BFDPROF`` in the created sessions under that interface.
A monitored static route conditions the installation to the RIB on the BFD session running state: when BFD session is up the route is installed to RIB, but when the BFD session is down it is removed from the RIB.
The following commands are available inside the configuration node:
.. clicmd:: ip route A.B.C.D/M A.B.C.D bfd [{multi-hop|source A.B.C.D|profile BFDPROF}]
Configure a static route for ``A.B.C.D/M`` using gateway ``A.B.C.D`` and use
the gateway address as BFD peer destination address.
.. clicmd:: ipv6 route X:X::X:X/M [from X:X::X:X/M] X:X::X:X bfd [{multi-hop|source X:X::X:X|profile BFDPROF}]
Configure a static route for ``X:X::X:X/M`` using gateway
``X:X::X:X`` and use the gateway address as BFD peer destination
address.
The static routes when uninstalled will no longer show up in the output of
the command show ip route or show ipv6 route, instead we must use the
BFD static route show command to see these monitored route status.
.. clicmd:: show bfd static route [json]
Show all monitored static routes and their status.
Example output:
::
Showing BFD monitored static routes:
Route groups:
rtg1 peer 172.16.0.1 (status: uninstalled):
2001:db8::100/128
Next hops:
VRF default IPv4 Unicast:
192.168.100.0/24 peer 172.16.0.1 (status: uninstalled)
VRF default IPv4 Multicast:
VRF default IPv6 Unicast:
Before applying bfdd rules to integrated daemons (like BGPd), we must
create the corresponding peers inside the bfd configuration node.
Here is an example of BFD configuration:
bfd peer 192.168.0.1 label home-peer no shutdown ! ! router bgp 65530 neighbor 192.168.0.1 remote-as 65531 neighbor 192.168.0.1 bfd neighbor 192.168.0.2 remote-as 65530 neighbor 192.168.0.2 bfd neighbor 192.168.0.3 remote-as 65532 neighbor 192.168.0.3 bfd !
Peers can be identified by its address (use multihop when you need
to specify a multi hop peer) or can be specified manually by a label.
Here are the available peer configurations:
bfd ! Configure a fast profile profile fast receive-interval 150 transmit-interval 150 ! ! Configure peer with fast profile peer 192.168.0.6 profile fast no shutdown ! ! Configure peer with fast profile and override receive speed. peer 192.168.0.7 profile fast receive-interval 500 no shutdown ! ! configure a peer on an specific interface peer 192.168.0.1 interface eth0 no shutdown ! ! configure a multihop peer peer 192.168.0.2 multihop local-address 192.168.0.3 shutdown ! ! configure a peer in a different vrf peer 192.168.0.3 vrf foo shutdown ! ! configure a peer with every option possible peer 192.168.0.4 label peer-label detect-multiplier 50 receive-interval 60000 transmit-interval 3000 shutdown ! ! configure a peer on an interface from a separate vrf peer 192.168.0.5 interface eth1 vrf vrf2 no shutdown ! ! remove a peer no peer 192.168.0.3 vrf foo
You can inspect the current BFD peer status with the following commands:
frr# show bfd peers
BFD Peers:
peer 192.168.0.1
ID: 1
Remote ID: 1
Status: up
Uptime: 1 minute(s), 51 second(s)
Diagnostics: ok
Remote diagnostics: ok
Peer Type: dynamic
Local timers:
Detect-multiplier: 3
Receive interval: 300ms
Transmission interval: 300ms
Echo receive interval: 50ms
Echo transmission interval: disabled
Remote timers:
Detect-multiplier: 3
Receive interval: 300ms
Transmission interval: 300ms
Echo receive interval: 50ms
peer 192.168.1.1
label: router3-peer
ID: 2
Remote ID: 2
Status: up
Uptime: 1 minute(s), 53 second(s)
Diagnostics: ok
Remote diagnostics: ok
Peer Type: configured
Local timers:
Detect-multiplier: 3
Receive interval: 300ms
Transmission interval: 300ms
Echo receive interval: 50ms
Echo transmission interval: disabled
Remote timers:
Detect-multiplier: 3
Receive interval: 300ms
Transmission interval: 300ms
Echo receive interval: 50ms
frr# show bfd peer 192.168.1.1
BFD Peer:
peer 192.168.1.1
label: router3-peer
ID: 2
Remote ID: 2
Status: up
Uptime: 3 minute(s), 4 second(s)
Diagnostics: ok
Remote diagnostics: ok
Peer Type: dynamic
Local timers:
Detect-multiplier: 3
Receive interval: 300ms
Transmission interval: 300ms
Echo receive interval: 50ms
Echo transmission interval: disabled
Remote timers:
Detect-multiplier: 3
Receive interval: 300ms
Transmission interval: 300ms
Echo receive interval: 50ms
frr# show bfd peer 192.168.0.1 json
{"multihop":false,"peer":"192.168.0.1","id":1,"remote-id":1,"status":"up","uptime":161,"diagnostic":"ok","remote-diagnostic":"ok","receive-interval":300,"transmit-interval":300,"echo-receive-interval":50,"echo-transmit-interval":0,"detect-multiplier":3,"remote-receive-interval":300,"remote-transmit-interval":300,"remote-echo-receive-interval":50,"remote-detect-multiplier":3,"peer-type":"dynamic"}
If you are running IPV4 BFD Echo, on a Linux platform, we also calculate round trip time for the packets. We display minimum, average and maximum time it took to receive the looped Echo packets in the RTT fields.
You can inspect the current BFD peer status in brief with the following commands:
frr# show bfd peers brief Session count: 1 SessionId LocalAddress PeerAddress Status ========= ============ =========== ====== 1 192.168.0.1 192.168.0.2 up
You can also inspect peer session counters with the following commands:
frr# show bfd peers counters
BFD Peers:
peer 192.168.2.1 interface r2-eth2
Control packet input: 28 packets
Control packet output: 28 packets
Echo packet input: 0 packets
Echo packet output: 0 packets
Session up events: 1
Session down events: 0
Zebra notifications: 2
peer 192.168.0.1
Control packet input: 54 packets
Control packet output: 103 packets
Echo packet input: 965 packets
Echo packet output: 966 packets
Session up events: 1
Session down events: 0
Zebra notifications: 4
frr# show bfd peer 192.168.0.1 counters
peer 192.168.0.1
Control packet input: 126 packets
Control packet output: 247 packets
Echo packet input: 2409 packets
Echo packet output: 2410 packets
Session up events: 1
Session down events: 0
Zebra notifications: 4
frr# show bfd peer 192.168.0.1 counters json
{"multihop":false,"peer":"192.168.0.1","control-packet-input":348,"control-packet-output":685,"echo-packet-input":6815,"echo-packet-output":6816,"session-up":1,"session-down":0,"zebra-notifications":4}
You can also clear packet counters per session with the following commands, only the packet counters will be reset:
frr# clear bfd peers counters
frr# show bfd peers counters
BFD Peers:
peer 192.168.2.1 interface r2-eth2
Control packet input: 0 packets
Control packet output: 0 packets
Echo packet input: 0 packets
Echo packet output: 0 packets
Session up events: 1
Session down events: 0
Zebra notifications: 2
peer 192.168.0.1
Control packet input: 0 packets
Control packet output: 0 packets
Echo packet input: 0 packets
Echo packet output: 0 packets
Session up events: 1
Session down events: 0
Zebra notifications: 4
The distributed BFD is the separation of the BFD protocol control plane from
the data plane. FRR implements its own BFD data plane protocol so vendors can
study and include it in their own software/hardware without having to modify
the FRR source code. The protocol definitions can be found at
bfdd/bfddp_packet.h header (or the installed
/usr/include/frr/bfdd/bfddp_packet.h).
To use this feature the BFD daemon needs to be started using the command line option :option:`--dplaneaddr`. When operating using this option the BFD daemon will not attempt to establish BFD sessions, but it will offload all its work to the data plane that is (or will be) connected. Data plane reconnection is also supported.
The BFD data plane will be responsible for:
- Sending/receiving the BFD protocol control/echo packets
- Notifying BFD sessions state changes
- Keeping the number of packets/bytes received/transmitted per session
The FRR BFD daemon will be responsible for:
- Adding/updating BFD session settings
- Asking for BFD session counters
- Redistributing the state changes to the integrated protocols (
bgpd,ospfdetc...)
BFD daemon will also keep record of data plane communication statistics with the command :clicmd:`show bfd distributed`.
Sample output:
frr# show bfd distributed
Data plane
==========
File descriptor: 16
Input bytes: 1296
Input bytes peak: 72
Input messages: 42
Input current usage: 0
Output bytes: 568
Output bytes peak: 136
Output messages: 19
Output full events: 0
Output current usage: 0
By default only informational, warning and errors messages are going to be displayed. If you want to get debug messages and other diagnostics then make sure you have debugging level enabled:
config log file /var/log/frr/frr.log debugging log syslog debugging
You may also fine tune the debug messages by selecting one or more of the debug levels:
.. clicmd:: debug bfd distributed Toggle BFD data plane (distributed BFD) debugging. Activates the following debug messages: * Data plane received / send messages * Connection events
.. clicmd:: debug bfd network Toggle network events: show messages about socket failures and unexpected BFD messages that may not belong to registered peers.
.. clicmd:: debug bfd peer Toggle peer event log messages: show messages about peer creation/removal and state changes.
.. clicmd:: debug bfd zebra Toggle zebra message events: show messages about interfaces, local addresses, VRF and daemon peer registrations.