bgp bfd and timers

[Mlex1]

Hello what's the purpose when we using bfd and at the same time using timers and does has any pros and cons.

for-ex

 i config bgp timer 5 10 and also in some of neighbors configure bfd what the purpose like this configuration or when we setting bfd we don't need to timers or apposite 

i want to understand thanks in advance 

[MHM Cisco World]

Bgp use keepalive and it timer in sec and bfd in mSec so sure bfd can faster detect peer dead before bgp.

MHM

[Mlex1]

one more thing does we need in topology p2p use bfd or it depends on convergence or how link failure important to us ?

[MHM Cisco World · Accepted solution]

-BFD use for B2B (back to back) only ? No you can use for B2B and multi-hop BGP 

-link failure in end cause BGP failed (if you use default 60/180 sec) then BGP need 60 sec before down Peer, with BFD it more faster in msec

what key factor of BFD? it HW offload, in High End router the BFD can completely run by line card not by CPU of router 

https://brbccie.blogspot.com/2014/06/everything-bfd.html

if you have more Q please ask 

[paul driver]

Hello
BFD is independent of any routing process so isn’t reliant on the limitations exposed on those processes as such it can be applied to many different network transport platforms.

[Mlex1]

i want to understand the reason for-ex in same cases use both.

or reason bfd detect problem early than bgp timer ? am i right. 

[simone-marangoni]

BFD can detect an issue earlier than BGP timer (msec vs sec) but the key difference is that BFD packet is a very light packet compared to BGP keepalive packet so you can exchange BFD at msec interval without impact CPU or bandwidth and leave the BGP timers to its default (60 180).