[c-nsp] OIR on 7600s: Pretty much evil?

[Blake Dunlap]

Good ole' "On Insert: Reload". Yeah the bus stalls are priceless, you're
best bet is to plan like you're taking down the router, and if it works, hey
you just saved some downtime, and are done early. That being said, at least
the actual crashes aren't terribly common, so you can do low risk stuff
without to much fear as long as there's redundancy. VRRP is a godsend for
those that do actual maintenance / changes to their network on a regular
basis.

You'd be surprised at how easy it is to take down a router by just being to
slow with the insert or removal, since its multiphase. I've had more issues
from that alone from certian technicians, than actual card or software bugs.

Once those contact pins touch on insert, or are broken on removal, you have
very little time to complete the move before processes freak out over the
bus stall, due to how the router protects itself, amusingly enough, from
more issues stemming from data corruption.

-Blake


On Wed, Nov 10, 2010 at 18:49, John Neiberger <jneiberger at gmail.com> wrote:

> On Wed, Nov 10, 2010 at 5:28 PM, Benjamin Lovell <belovell at cisco.com>
> wrote:
> > It's true. Bad things can happen. Primary one is buss stall. They are not
> > supposed to happen anymore but there are bugIDs out there that prove they
> > do. During buss stall we can't do forwarding lookups to PFC(pretty sure
> DFC
> > lookups still work). Even worse is that during buss stall interrupts are
> > disabled so packets can't be punted to the control plane and BFD packets
> > which are generated in interrupt context can't be sent.
> >
> > Usually these things happen for a short enough period of time that the
> > effects are minor or completely unnoticed unless you are running some
> things
> > with tight timers like BFD tuned down, OSPF fast hellos, etc
> >
> > -Ben
>
> I know for a fact that buss stalls happen because we saw it happen
> last night!  ;)
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