[AusNOG] BGP hold timer values

[McDonald Richards]

Re: BFD on eBGP

I think you'll find most will support it ad-hoc if requested but be
prepared for compatibility issues.

Ones I can think of:

IPv4/IPv6 sessions (one comes up but the other refuses)
Single-hop vs Multi-hop implementations

These may be platform specific but if you want the feature and your
provider is focused on providing great service, they'll likely work with
you to make it work after some tweaking.

Re: timers

I am going to go from memory here, which is a little rusty, and recall that
the lowest set peer wins the timer battle (peer with lowest setting
negotiates for the session). If you want your EBGP to fall over faster then
set it lower and your provider should negotiate to your settings. This was
a fairly common recommendation I made in a previous life.

If you set these down and start seeing flaps, someone's CPU is too busy.

Macca




On Tue, Jan 27, 2015 at 3:09 PM, Alex Samad - Yieldbroker <
Alex.Samad at yieldbroker.com> wrote:

>  Thanks.
>
>
>
> Brings me back to BFD, how many providers use this. Is anyone using this
> with eBGP
>
>
>
> A
>
>
>
> *From:* Andrew Jones [mailto:Andrew.Jones at optus.com.au]
> *Sent:* Wednesday, 28 January 2015 9:33 AM
> *To:* Alex Samad - Yieldbroker; Tom Berryman
> *Cc:* ausnog at lists.ausnog.net
> *Subject:* RE: [AusNOG] BGP hold timer values
>
>
>
> There is a lot more factors in play for BGP to converge than just
> hello/hold timers.
>
>
>
> This is a good article to read:
>
>
>
> http://blog.ine.com/2010/11/22/understanding-bgp-convergence/
>
>
>
> Cheers,
>
>
>
> Andrew Jones
>
>
>
> *From:* AusNOG [mailto:ausnog-bounces at lists.ausnog.net
> <ausnog-bounces at lists.ausnog.net>] *On Behalf Of *Alex Samad - Yieldbroker
> *Sent:* Tuesday, 27 January 2015 11:19 PM
> *To:* Tom Berryman
>
> *Cc:* ausnog at lists.ausnog.net
> *Subject:* Re: [AusNOG] BGP hold timer values
>
>
>
> Hi
>
>
>
> I will have to monitor that.
>
>
>
> We suffered from an outage recently, with a provider we have 2 links
> with.  We have multiple providers.
>
> As a review of the incident the business asked about the 3m hold timer. In
> theory the way I read it, is the routes could be held for up to 3 min
> whilst the link is down…
>
>
>
>
>
> One of the questions was why did it take soo long ~ 8-9min for traffic to
> appear on the other link.  Waiting for feedback on that
>
> I am presuming with a lower hold timer/keep alive I can get pretty fast
> response as its only on this providers network I am failing over.
>
>
>
> Alex
>
>
>
>
>
> *From:* Tom Berryman [mailto:Tom at connectivityit.com.au
> <Tom at connectivityit.com.au>]
> *Sent:* Tuesday, 27 January 2015 11:09 PM
> *To:* Alex Samad - Yieldbroker
> *Cc:* David Hughes; ausnog at lists.ausnog.net
> *Subject:* Re: [AusNOG] BGP hold timer values
>
>
>
> There is a bit more than just a few extra packets (as your cost) - BGP
> can/does have notable CPU impact on low-mid range routing gear.
>
>
>
> With eBGP, you are talking propagation of your routes to the internet, so
> not all of the internet is going to see your changes for maybe up to 180
> seconds. That said, it's likely most of it will be sooner than that.
>
>
>
> Tom
>
>
>
>  On 27 Jan 2015, at 11:01 pm, Alex Samad - Yieldbroker <
> Alex.Samad at yieldbroker.com> wrote:
>
>
>
> Hi
>
> Okay its eBGP, currently have 4 providers, some with multiple connections.
> So I am thinking 6 / 20 might be good for me, business requirement for
> approx. 30sec response.
> I am presuming all I am looking at is extra BGP packets .. every 6 sec
> compared to 1 min..
>
>
> Alex
>
> -----Original Message-----
> From: David Hughes [mailto:david at hughes.com.au <david at hughes.com.au>]
> Sent: Tuesday, 27 January 2015 9:37 PM
> To: Alex Samad - Yieldbroker
> Cc: ausnog at lists.ausnog.net
> Subject: Re: [AusNOG] BGP hold timer values
>
>
> I gave a lightning talk about this sort of thing a while ago at an
> APRICOT.  I just
> googled to find the slides and can now see just how many years ago it was.
> Gotta say I'm feeling old :)
>
> But, it's probably still relevant although the defaults may have changed.
> This
> reflected what we were running at the time - and we were trying to be
> pretty aggressive.
>
> http://archive.apnic.net/meetings/21/docs/sigs/routing/routing-
> pres-hughes-bgp.pdf
>
> For reference I'm currently happy to run
>
> eBGP
>
> : 10 / 30
> iBGP
>
> : 5 / 15
>
> And I'd run this even to a single upstream.  If it fails at least you'll
> have
> something in your logs to say why you fell off the net for a while.  Silent
> failures are a bugger to troubleshoot.
>
>
> Thanks
>
> David
> ...
>
>
>
> On 27/01/2015, at 6:47 PM, Alex Samad - Yieldbroker
> <Alex.Samad at yieldbroker.com> wrote:
>
> Hi
>
> I'm wonder what is considered "best practice" or good/responsible hold
>
> timer values for BGP.
>
>
> Currently I'm set at 3m, but I am considering lowering this to 30s and keep
>
> alive down to 20s, potentially even lower. Or if possible to use BFD & BGP,
> what's the uptake on BFD ?
>
>
> Alex
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