--> BFD stands for bidirectional forwarding detection.
--> BFD is used to detect link failures very fastly compared to normal hello/hold down timers which are used in routing protocols.
--> BFD is independent of any routing protocol such as EIGRP/OSPF/BGP/static.
--> Depending on the routing protocol, we can lower the timers to achieve fast failure detection. e.g. in the case of OSPF, the lowest dead time can be one second and one can set the hello interval as low as 50ms.
--> But this lowering the hello and hold down timer leads to higher CPU utilization and unnecessarily waste the link bandwidth.
--> BFD is a UDP-based protocol that provides fast independent detection of layer-3 next hop failures in milliseconds.
--> BFD uses smaller hello packets similar to any routing protocol hello packets used to detect link failures.
--> BFD can be configured in two modes i) Asynchronous ii) Demand
--> To configure BFD on Cisco router, we need to go to the interface where you want to detect the link failure and use the following command
Ex: interface fa0/0
bfd interval 30 min_rx 20 multiplier 3
Note:
--> 30 is the hello timer which specifies the frequency of BFD packets sent by the router.
--> 20 is the receive-timer which represent the minimum interval between packets accepted from BFD peers.
--> 3 is the multiplier which is the number of BFD hello packets can be lost before BFD peer id declared down.
--> BFD is used to detect link failures very fastly compared to normal hello/hold down timers which are used in routing protocols.
--> BFD is independent of any routing protocol such as EIGRP/OSPF/BGP/static.
--> Depending on the routing protocol, we can lower the timers to achieve fast failure detection. e.g. in the case of OSPF, the lowest dead time can be one second and one can set the hello interval as low as 50ms.
--> But this lowering the hello and hold down timer leads to higher CPU utilization and unnecessarily waste the link bandwidth.
--> BFD is a UDP-based protocol that provides fast independent detection of layer-3 next hop failures in milliseconds.
--> BFD uses smaller hello packets similar to any routing protocol hello packets used to detect link failures.
--> BFD can be configured in two modes i) Asynchronous ii) Demand
--> To configure BFD on Cisco router, we need to go to the interface where you want to detect the link failure and use the following command
Ex: interface fa0/0
bfd interval 30 min_rx 20 multiplier 3
Note:
--> 30 is the hello timer which specifies the frequency of BFD packets sent by the router.
--> 20 is the receive-timer which represent the minimum interval between packets accepted from BFD peers.
--> 3 is the multiplier which is the number of BFD hello packets can be lost before BFD peer id declared down.
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