[CentOS] oops, or how to bring a datacenter router down with one setting

Fri Feb 10 21:58:56 UTC 2012
Les Mikesell <lesmikesell at gmail.com>

On Fri, Feb 10, 2012 at 3:40 PM, <m.roth at 5-cent.us> wrote:

> Devin Reade wrote:
> <snip>
> > I do have clusters where bonding is in use but those have helped not so
> > much in avoiding NIC failures as they do in allowing the machines
> > to continue operating as the network team brings down part of the
> > redundant switch network for maintenance (or to replace a failed switch,
> > or when some fool decides that they can unplug a network cable
> > briefly so that they can move other cables around).
> >
> Now wait a minute - I would dearly love to disconnect some cables we have
> in a shared rack downstairs in the datacenter - it's a rats' nest, and
> more than half ain't ours, and every single time I have to do something in
> the back, I'm deathly afraid I'm going to pull out somebody's power,
> or....

Do you really want to double the size of the mess to make it a little safer
to move one thing?   Redundant power connections normally do work with only
a little attention to grounding and that the connections really do go to
separate circuits/UPSs.  But with NICs, you have to be very careful that
the switch ports are configured to match so you are even more likely to
break things by moving them around.    It's not impossible, but rarely
worthwhile if you don't need the combined bandwidth.   But the real lesson
here is to not do something for the first time in a place where mistakes
will cause big trouble.

   Les Mikesell
     lesmikesell at gmail.com