Questions about BFD for BGP

Answered Question
Jul 7th, 2008

I have two OC3 connections to my ISP, one primary and one backup. I am also running BGP. Both routers are 7204VXRs running 12.4(11)T series and are located in physically seperate buildings for survivability reasons. They are connected via fiber and are on seperate networks.

Currently, I have a VERY VERY long wait for BGP to settle down after a loss of the primary OC3.

To combat this, I was looking into using BFD. The only problem is BFD can only be configured on an Ethernet-type port. This means I cannot configure it on my POS port.

How would I setup BFD to make this work? My plan is to configure BFD on the gig0/1 ports of both routers and setup the neighbor fall-over bfd command to point to the BGP neighbor of each respective router.

Would this work?

I have this problem too.
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Correct Answer by mohammedmahmoud about 8 years 5 months ago

Hi,

You are very welcomed, BFD is currently only supported on Ethernet, FastEthernet, and GigabitEthernet interfaces, thus the router on which you want to use BFD with BGP, the interface connected to its neighbor must be an Ethernet interface, i don't know how you are setting all your routers, but this is how it should go.

I hope that i've been informative.

BR,

Mohammed Mahmoud.

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mohammedmahmoud Mon, 07/07/2008 - 10:38

Hi,

You'll need the following:

Router(config-if)# bfd interval min_rx multiplier

Router(config-if)# bfd neighbor x.x.x.x

Router(config-router)# neighbor x.x.x.x fall-over bfd

But note a critical issue, BFD is supported for single hop neighbors ONLY - Can't be used when peering with loopbacks.

BR,

Mohammed Mahmoud.

cybrsage Mon, 07/07/2008 - 10:44

Thanks. Those are the commands I found.

However, since BFD will only work with ethernet type ports (gigabit ethernet in my case) and my BGP connection is via a POS port, will it function properly?

My guess is that it will, since the router with the gigabit ethernet port and pos port does not count as a hop, but I want to make sure.

Correct Answer
mohammedmahmoud Mon, 07/07/2008 - 12:11

Hi,

You are very welcomed, BFD is currently only supported on Ethernet, FastEthernet, and GigabitEthernet interfaces, thus the router on which you want to use BFD with BGP, the interface connected to its neighbor must be an Ethernet interface, i don't know how you are setting all your routers, but this is how it should go.

I hope that i've been informative.

BR,

Mohammed Mahmoud.

cybrsage Tue, 07/08/2008 - 03:49

Thank you. It seems VERY limited, since I would assume most people are not ISPs and therefor use BGP on their connection to their ISP. This, naturally, would not be an ethernet port.

Oh well, I had high hopes for reducing the time BGP takes to converge.

mohammedmahmoud Tue, 07/08/2008 - 04:02

Michael,

It is a relatively new feature, and i believe that it will be enhanced more and more in the future.

BR,

Mohammed Mahmoud.

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