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ASK THE EXPERT - BIIDIRECTIONAL FORWARDING DETECTION (BFD)

Welcome to the Cisco Networking Professionals Ask the Expert conversation. This is an opportunity to discuss with Cisco expert Aamer Akhter about Bidirectional Forwarding Detection (BFD) and how it is used to quickly detect IP forwarding failures. Aamer is currently working as a technical marketing engineer in the areas of Network Virtualization, Wan-Optimization and router instrumentation. He is CCIE certified (# 4543). Aamer is also the vice-chair of the Certification Work Group of the MFA Forum.

Remember to use the rating system to let Aamer know if you have received an adequate response.

Aamer might not be able to answer each question due to the volume expected during this event. Our moderators will post many of the unanswered questions in other discussion forums shortly after the event. This event lasts through February 23, 2007. Visit this forum often to view responses to your questions and the questions of other community members.

19 REPLIES

Re: ASK THE EXPERT - BIIDIRECTIONAL FORWARDING DETECTION (BFD)

hi,

which protocols supprot BFD and perticular on which platform i can enable BFD?

is it good idea for enabling on the WAN connectivity? and what is the minimum bandwidth requirement for it?

and i also want to know the benifites of the BFD feature in the Transport Network like SONET SDH...?

Cisco Employee

Re: ASK THE EXPERT - BIIDIRECTIONAL FORWARDING DETECTION (BFD)

BFD for WAN is an ideal placement. Keep in mind that for IOS today only Ethernet interfaces are supported. The bandwidth per packet is extremely small (less 100B), but will depend on your rate of packet transmission.

Protocols currently supported in IOS: OSPF, ISIS, BGP (single hop)

For IOS-XR, both POS and Ethernet interfaces are supported.

Protocols currently supported in IOS-XR: OSPF, ISIS, BGP (single hop), statics, MPLS-FRR

BFD is not only important in cases where there is a L2 switch in between your L3 routers, but is useful for other cases also (as in SONET/SDH that already provide Loss of Signal indication) where a check of the forwarding plane can be useful.

Re: ASK THE EXPERT - BIIDIRECTIONAL FORWARDING DETECTION (BFD)

hi akhter,

thank you very much for your reply...

now one more thing is: BFD works at which layer?

and will you please provide some link where i can find some confugiration or some explanation with SONET/SDH/ATM... as right now i am working for the same topology and would like to test it...

and also want to understand the BFD between two devices if they are running the HSRP... like will BFD helpfull to detect the fast failover when you have HSRP in your network?

thanks and regards

Devang

Cisco Employee

Re: ASK THE EXPERT - BIIDIRECTIONAL FORWARDING DETECTION (BFD)

Devang,

take a look athe following URL regarding BFD and HSRP:

http://cco/en/US/partner/products/ps6441/products_feature_guide09186a0080784f53.html

New Member

Re: ASK THE EXPERT - BIIDIRECTIONAL FORWARDING DETECTION (BFD)

hi,

can u provide information about e-guide book to study for Cisco 642-381 exam? Plz i am in big problem for this exam, help me out from this problem.

with thanks

sabuz

Cisco Employee

Re: ASK THE EXPERT - BIIDIRECTIONAL FORWARDING DETECTION (BFD)

Sabuz,

This forum is for BFD Q&A. Please take a look at http://wwww.cisco.com/go/ccie.

Regards,

New Member

Re: ASK THE EXPERT - BIIDIRECTIONAL FORWARDING DETECTION (BFD)

Are there plans to support BFD in the 3750 Metro switches? BFD would be ideal in these switches as the only option we have for improved failure detection at this point in time is fast OSPF timers, where OSPF is in use.

BFD seems to be supported in a limited range of hardware at the moment.

Cisco Employee

Re: ASK THE EXPERT - BIIDIRECTIONAL FORWARDING DETECTION (BFD)

Hi,

BFD is on the current year (2nd half) roadmap for the 3750.

Please be advised that roadmaps are subject to change and it is highly recommended to notify your cisco representative about this need so that it can be correctly prioritized.

Re: ASK THE EXPERT - BIIDIRECTIONAL FORWARDING DETECTION (BFD)

hi akhter,

I tried to search some configuration notes but i didnt find it... i got the following link but its not working:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1838/products_feature_guide09186a0080134a41.html.

will you please provide some other link for that?

regards

Devang

Cisco Employee

Re: ASK THE EXPERT - BIIDIRECTIONAL FORWARDING DETECTION (BFD)

New Member

Re: ASK THE EXPERT - BIIDIRECTIONAL FORWARDING DETECTION (BFD)

Hi Aamer,

I want to run BFP for OSPF over an EoMPLS tunnel, ie over SP network. Can I still get subsecond convergence? Service provider is doing policing at their end.

Thanks,

Prakash

New Member

Re: ASK THE EXPERT - BIIDIRECTIONAL FORWARDING DETECTION (BFD)

There could be a problem with your application, BFD hello packet is UDP packet with TTL set to 255, if MPLS changes TTL, the BFD won't form neighbor relationship.

BFD is intended to work over directly connected L3 link.

Cisco Employee

Re: ASK THE EXPERT - BIIDIRECTIONAL FORWARDING DETECTION (BFD)

Prakash,

Technically, there is no reason why BFD would not work over EoMPLS. The TTL problem pointed out earlier does not apply as EoMPLS is at layer 2 and the IP TTL of the customer traffic is not decremented.

Couple of things that I would be wary of:

* delay characteristics of the path (lets say the path in the SP changes all of a sudden and the packets your were expecting start arriving later than expected)

* policing on SP side. You'll need to make sure that you have a shaping policy implemented that prevents the SP from dropping your traffic (or get agreement from SP not to drop prec 6 traffic first, as that is what BFD will be under). Your shaping policy should make sure that BFD has a clear policy that will allow it to send packets without worry of dropping.

Regards,

New Member

Re: ASK THE EXPERT - BIIDIRECTIONAL FORWARDING DETECTION (BFD)

Thanks Amer...We tested it and it is working fine...(just one drop..:) :)

Prakash

Cisco Employee

Re: ASK THE EXPERT - BIIDIRECTIONAL FORWARDING DETECTION (BFD)

Prakash,

Please make sure that the detect time you are using takes into account a minor reconvergence within the SP cloud. Such a reconvergence (could be a couple of seconds or sub-seconds depending on what the SP has done) would be be a indication of a major failure at your level and you may not want to take corrective action in these cases.

Re: ASK THE EXPERT - BIIDIRECTIONAL FORWARDING DETECTION (BFD)

Silver

Re: ASK THE EXPERT - BIIDIRECTIONAL FORWARDING DETECTION (BFD)

And here is the link without the partner login requirement:

http://www.cisco.com/en/US/products/ps6017/products_feature_guide09186a00803fbe87.html

New Member

Re: ASK THE EXPERT - BIIDIRECTIONAL FORWARDING DETECTION (BFD)

hi , i m looking additional infomation of the following poduct , CVPN3000-UKITA-K9.

reg

SA

Cisco Employee

Re: ASK THE EXPERT - BIIDIRECTIONAL FORWARDING DETECTION (BFD)

Hello,

This is the Q&A session for BFD. You may find some information on the VPN 3000 at:

http://www.cisco.com/en/US/products/hw/vpndevc/ps2284/index.html

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