# Bidirectional Forwarding Detection (BFD)
**URL:** https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280
**Category:** Lessons Discussion
**Created:** [December 29, 2016, 8:02pm UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280 "2016-12-29T20:02:40Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [December 29, 2016, 8:02pm UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/1 "2016-12-29T20:02:40Z")
This topic is to discuss the following lesson:
[https://networklessons.com/cisco/ccie-enterprise-infrastructurebidirectional-forwarding-detection-bfd/](https://networklessons.com/cisco/ccie-enterprise-infrastructurebidirectional-forwarding-detection-bfd/)
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### Author:  [@shinuvarghesea](https://forum.networklessons.com/u/shinuvarghesea)
#### Post date: [July 31, 2015, 4:13pm UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/2 "2015-07-31T16:13:31Z")
Really great article. Always you put new topics and explained it in very easy manner.
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### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [July 31, 2015, 4:32pm UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/3 "2015-07-31T16:32:57Z")
Thanks Shinu!
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### Author:  [@mauroaldair](https://forum.networklessons.com/u/mauroaldair)
#### Post date: [July 31, 2015, 7:10pm UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/4 "2015-07-31T19:10:31Z")
Hello Rene,
Nice article about BFD.
Mauro.
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### Author:  [@phase19](https://forum.networklessons.com/u/phase19)
#### Post date: [August 1, 2015, 8:23am UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/5 "2015-08-01T08:23:11Z")
Hi, thanks for the great simplification of the protocol. Are there any other quirks to it that a network engineer should be aware of? Also, what other protocols does it support? i.e. OSPF, EIGRP, HSRP etc.? Can you elaborate on more examples…?
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### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [August 1, 2015, 11:38am UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/6 "2015-08-01T11:38:45Z")
Hi Dhananjay,
Not any that I can think of now, it’s pretty straight forward. The protocols that are supported are OSPF, EIGRP, IS-IS, BGP, MPLS LDP, HSRP and VRRP but it’s possible that not all platforms support them.
The configuration of IS-IS and EIGRP is the same as OSPF, you only have to use the “bfd all-interfaces” command. BGP is a bit different:
router bgp 40000
neighbor x.x.x.x fall-over bfd
For HSRP you need to use the “standby bfd all-interfaces” command.
Rene
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### Author:  [@phase19](https://forum.networklessons.com/u/phase19)
#### Post date: [August 1, 2015, 6:59pm UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/7 "2015-08-01T18:59:51Z")
Thanks Rene.
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### Author:  [@dreamtfk](https://forum.networklessons.com/u/dreamtfk)
#### Post date: [August 13, 2015, 2:15pm UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/8 "2015-08-13T14:15:29Z")
So in this example BFD wouldn’t really be any benefit since it is a daisy chain correct? However in a network with redundancy if a link went down then OSPF would fail over to a secondary link much faster if using BFD. Am I saying that correct?
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### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [August 13, 2015, 4:08pm UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/9 "2015-08-13T16:08:43Z")
Hi Emir,
The convergence time basically consists of the link failure detection + the time it takes for OSPF to run SPF and update the routing table / forwarding table. In my example, detecting the link failure took 28 seconds. Running SPF / updating the routing table (and forwarding table) might take ~ 50ms. By implementing BFD, our link failure detection is reduced from 28 seconds to ~150ms.
In my example I only have two routers so when something goes on, it’s game over 🙂
Implementing BFD is useful if you have multiple OSPF routers and redundant links.
Rene
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### Author:  [@dreamtfk](https://forum.networklessons.com/u/dreamtfk)
#### Post date: [August 13, 2015, 4:16pm UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/10 "2015-08-13T16:16:30Z")
Understood, thanks.
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### Author:  [@mangatoea](https://forum.networklessons.com/u/mangatoea)
#### Post date: [August 16, 2015, 11:36pm UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/11 "2015-08-16T23:36:54Z")
Great stuff! Thanks Rene for clear example
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### Author:  [@hamoodrehman87](https://forum.networklessons.com/u/hamoodrehman87)
#### Post date: [August 18, 2015, 1:36am UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/12 "2015-08-18T01:36:27Z")
Rene,
What type of router and IOS did you use in the lab?
Please advice.
Thanks
Hamood
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### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [August 18, 2015, 10:41am UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/13 "2015-08-18T10:41:10Z")
Hi Hamood,
I used 2811 routers with IOS 15.x.
Rene
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### Author:  [@shannon.sariman](https://forum.networklessons.com/u/shannon.sariman)
#### Post date: [October 16, 2015, 6:45am UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/14 "2015-10-16T06:45:32Z")
Hi Rene,
Many thanks for this lesson! I am enlightened!
Rgds,
Shannon
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### Author:  [@mgthetpinesoe](https://forum.networklessons.com/u/mgthetpinesoe)
#### Post date: [October 22, 2015, 8:56am UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/15 "2015-10-22T08:56:20Z")
Easy to understand well , great one of articles.
If devices are using link aggregation (ether-channel) , can we use BFD ?
Thanks, Rene
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### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [October 23, 2015, 12:41pm UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/16 "2015-10-23T12:41:17Z")
Hi Thet,
Good question. There are some models and IOS versions that support this but most don’t.
Rene
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### Author:  [@mario\_ramales](https://forum.networklessons.com/u/mario_ramales)
#### Post date: [January 4, 2016, 11:53pm UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/17 "2016-01-04T23:53:22Z")
Would be nice if you could include a t-shoot section. I had an issue with BFD and had to run some “show bfd x” commands.
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### Author:  [@abdelrahman.rabie](https://forum.networklessons.com/u/abdelrahman.rabie)
#### Post date: [March 6, 2016, 1:31pm UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/18 "2016-03-06T13:31:32Z")
I would like to share new info . when you put different time intervals and multipliers between two neighbors, the greater value in interval and multipliers will be taken between neighbors.
this case I faced when configure BFD between Cisco and Juniper — in Cisco time interval from (50 – 999) in juniper time interval ( 1 — 255000 ) and recommended greater than 1000 ms .
I got it by try and error 🙂
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### Author:  [@casper.visser](https://forum.networklessons.com/u/casper.visser)
#### Post date: [April 16, 2016, 6:34am UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/19 "2016-04-16T06:34:02Z")
Hi Rene
I have a straight forward topology:
Router(r5)-switch-trunk-switch-router(r6)
R5: int fa 0/0 - 192.168.1.1/24
OSPF 1 area 0
R6: int fa 0/0 - 192.168.1.2/24
OSPF 1 area 0
Routers can ping each other and ospf neighbours form.
I configured this string on fa 0/0 int on both routers:
`bfd interval 150 min_rx 150 multiplier 3`
The issue is the bfd neighbourship stays down:
State bit: AdminDown
I’ve tried shutting and unshutting the interfaces etc but nothing changes the state, any ideas?
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### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [April 20, 2016, 9:33pm UTC](https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/20 "2016-04-20T21:33:40Z")
Hi Casper,
On what platform/routers did you try this? It doesn’t work for me on the IOSv images in Cisco VIRL but it does on real hardware.
Rene
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