Manual:Routing/BFD
Summary
Bidirectional Forwarding Detection (BFD) is a low-overhead and short-duration protocol intended to detect faults in the bidirectional path between two forwarding engines, including physical interfaces, sub-interfaces, data link(s), and to the extent possible the forwarding engines themselves, with potentially very low latency. It operates independently of media, data protocols and routing protocols.
BFD is basically a hello protocol for checking bidirectional neighbor reachability. It provides sub-second link failure detection support. BFD is not routing protocol specific, unlike protocol hello timers or such.
Standards and Technologies:
- RFC 5880 Bidirectional Forwarding Detection (BFD)
- RFC 5881 BFD for IPv4 and IPv6 (Single Hop)
- RFC 5882 Generic Application of BFD (Single Hop)
- RFC 5883 BFD for Multihop Paths
- RFC 5884 BFD for MPLS LSPs
- RFC 5885 BFD VCCV
Requirements
RouterOS 4.4 or newer with routing package installed.
Features supported
- asynchronous mode [1]
- BFD timer and detection multiplier configuration per interface;
- enabling BFD for OSPF interfaces
- enabling BFD for BGP peers
- single hop IPv4 and IPv6 transport [2]
- multihop IPv4 and IPv6 transport [3]
Features not yet supported
- echo function
- on-demand mode
- authentication
Configuration
BFD configuration should be added in different places as required
BFD timer configuration
Sub-menu: /routing bfd interface
Properties
| Property | Description |
|---|---|
| interface (string; Default: ) | Interface name to which BFD timers will be applied |
| interval (decimal [0.01 .. 10]sec; Default: 0.2sec) | |
| min-rx (decimal [0.01..10]sec; Default: 0.2sec) | |
| multiplier (integer [1..100]; Default: 5) |
BFD neighbor status
Sub-menu: /routing bfd neighbor
Read-only properties
| Property | Description |
|---|---|
| actual-tx-interval (decimal) | |
| address (IP | IPv6) | IP/IPv6 address of the neighbor |
| desired-tx-interval (decimal) | |
| hold-time (time) | |
| interface (string) | interface name on which BFD neighbor is reachable |
| multihop (yes | no) | Whether neighbor is multiple hops away |
| multiplier (integer) | |
| packets-rx (integer) | Number of received packets |
| protocols (ospf | bgp) | For which protocols BFD is used, currently only OSPF and BGP are possible. |
| remote-min-rx (decimal) | |
| required-min-rx (decimal) | |
| state (up | down) | Shows the current BFD state |
| state-changes (integer) | Number of state changes occurred between the neighbors |
| up (yes | no) | Whether link to the neighbor is up |
| uptime (time) | Link uptime |
Example of BFD neighbor. Neighbor is used by OSPF and is directly connected.
[admin@R3-493G] /routing bfd neighbor> print detail
Flags: U - up
0 U state=up address=10.5.101.1 interface=ether1 protocols=ospf multihop=no
state-changes=1 uptime=12s desired-tx-interval=0.2sec
actual-tx-interval=0.2sec required-min-rx=0.2sec remote-min-rx=0.2sec
multiplier=5 hold-time=1sec packets-rx=76 packets-tx=77
OSPF
There is only one parameter per OSPF interface to enable BFD
/routing ospf interface add interface=all use-bfd=yes
BGP
Similar to OSPF, only one option per BGP peer to enable BFD
/routing bgp peer add remote-address=x.x.x.x remote-as=xxxxx use-bfd=yes
Interoperability
For interoperability with Cisco make sure to disable echo mode (it is enabled on Cisco by default), since it's not supported on MT.
To do that, on Cisco in interface configuration mode type:
no bfd echo
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