jumbograms (& em) & nfs a no go

[Barney Wolff]

On Fri, Oct 31, 2003 at 12:56:11AM -0800, Terry Lambert wrote:
> Michal Mertl wrote:
> > I then left one computer at 4.9 and upgraded the other to 5.0. When I
> > mount a partition from 5.0 machine I found out, that copying reliably
> > works only from 5.0 to 4.9. The other way around I see messages 'em0:
> > discard oversize frame (ether type 800 flags 3 len 67582 > max 6014)' on
> > 5.0 and the copying stalls. On 4.9 machine I later see 'nfs server
> > 10.0.0.2:/usr: not responding'. The interface is stuck for some time - can
> > be revived by changing mtu back to 1500 and down/up sequence.
> 
> Implies the sending host is not honoring the MTU restriction when
> deciding whether or not to frag packets.

67582 looks awfully bogus even as a pre-frag length.  How could that come
over the wire?

-- 
Barney Wolff         http://www.databus.com/bwresume.pdf
I'm available by contract or FT, in the NYC metro area or via the 'Net.