What is the function of bfd(bi-directional forwarding detection) and how is it used on Cisco routers?

[Martorossi]

What is the function of bfd(bi-directional forwarding detection) and how is it used on Cisco routers?

What is meant by bfd state of a port is down, and how can it be rectified?

[Nagendra Kumar Nainar]

Hi,

What is the function of bfd(bi-directional forwarding detection) and how is it used on Cisco routers?

BFD is used for fast failure detection that can help improvise network convergence. Assume 2 routers are connected over L2 switch and were running OSPF (or otehr IGP). If the link from one router to the switch (or the router itself) goes down, it will take a long time to identify the failure depending on the IGP timer configuration.

BFD is a light weight protocol that will be exchanged at a very fast rate (like 4 packets every second) and can detect the failure within few msec and intimate to IGP to take any necessary action (like triggering FRR or advertsing the link state change etc).

What is meant by bfd state of a port is down, and how can it be rectified?

Can you share the output to see what error is it?.

-Nagendra

[Martorossi]

On a huawei router

<R2-IB-UK-ETNE40E>dis bfd se all | in 3/0/5

--------------------------------------------------------------------------------

Local Remote PeerIpAddr      State     Type        InterfaceName               

--------------------------------------------------------------------------------

695   696    192.168.101.138 Down      S_IP_IF     GigabitEthernet3/0/5

--------------------------------------------------------------------------------

     Total UP/DOWN Session Number : 44/1

<R2-IB-UK-ETNE40E>  

I don't know the command for cisco router.