[c-nsp] Routing around errors

[Keegan Holley]

I've always been nervous about automating something like, but to each his
own.  There are a few different solution that poll specifically with
performance in mind.  You should also be able to set the generic pollers to
trap based on threshold.  From there I'd just let a lowly human decide what
to do.  My concerns with automation have been things like: How do we make
sure the secondary path is clean and has enough bw to handle the load? How
do we move things back once the issue is gone?  How do we prevent
automation from disabling both links if the secondary is down or unusable?
 Granted I haven't done a wealth of research  on tools that would do this,
but usually a good NOC will be able to figure something like this out and
fix it in 15-20 minutes.  Automation may take a while to implement and
perfect (even if it's purchased) only to save me 20 minutes of dropped
packets.  YMMV though.

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2011/12/9 Geoffrey Pendery <geoff at pendery.net>

> We've seen an old nuisance issue becoming more prevalent lately - at
> dual-homed sites one of the circuits will run errors, but not bad
> enough to drop the routing protocol neighbor (OSPF in our case).
>
> So a site with one good circuit and one error-heavy circuit will
> continue to route traffic over the circuit with errors.  I'm curious
> what solutions are prevalent out there, anybody want to weigh in?
>
> Tune the hellos tight enough in the hopes of dropping the neighbors?
> PfR/OER?
> Alerts from monitoring system followed by manual intervention?
> EEM scripts checking the counters?
>
>
> Thanks,
> Geoff
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