Multi-homed clients and BGP timers

Olof Kasselstrand olof.kasselstrand at
Mon May 25 03:38:09 CDT 2009

We have customers in the same way you do. We only use Cisco (both pop
routers and managed cpe) and use

neighbor timers 5 15

on the pop routers with great success. We haven't found any drawback so far.

// OK

On Sat, May 23, 2009 at 12:45 AM, Steve Bertrand <steve at> wrote:
> Hi all,
> I've got numerous single-site 100Mb fibre clients who have backup SDSL
> links to my PoP. The two services terminate on separate
> distribution/access routers.
> The CPE that peers to my fibre router sets a community, and my end sets
> the pref to 150 based on it. The CPE also sets a higher pref for
> prefixes from the fibre router. The SDSL router to CPE leaves the
> default preference in place. Both of my PE gear sends default-originate
> to the CPE. There is (generally) no traffic that should ever be on the
> SDSL link while the fibre is up.
> Both of the PE routers then advertise the learnt client route up into
> the core:
> *>i208.70.107.128/28
>                       0    150      0 64762 i
> * i                    0    100      0 64762 i
> My problem is the noticeable delay for switchover when the fibre happens
> to go down (God forbid).
> I would like to know if BGP timer adjustment is the way to adjust this,
> or if there is a better/different way. It's fair to say that the fibre
> doesn't 'flap'. Based on operational experience, if there is a problem
> with the fibre network, it's down for the count.
> While I'm at it, I've got another couple of questions:
> - whatever technique you might recommend to reduce the convergence
> throughout the network, can the same principles be applied to iBGP as well?
> - if I need to down core2, what is the quickest and easiest way to
> ensure that all gear connected to the cores will *quickly* switch to
> preferring core1?
> Steve

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