When bringing down an interface with ifdown, it hangs on the
check_default_route in ifdown-post. Afaics this evaluates to the
following code:

return `/sbin/route -n|gawk 'BEGIN{r=1} $3=="0.0.0.0" && $4=="UG" {r=0}
END{print r}'`

When I do this at the prompt, I can see the gawk call taking 99% of the
cpu time. I'm not sure what causes this, but it is 99% reproducable on
this particular box. I haven't seen it on my Intel boxes yet.

Information on the machine:

DEC Multia (ev4 166MHz (UDB))
32 MB RAM
300 MB SCSI HD