RE: [Xen-users] XCP ethernet jumbo frames????

[Rob Hoes <Rob.Hoes@xxxxxxxxxx>]

Jumbo frame support was still in development when XCP 0.5 was released. Though 
it may work, you probably should not rely on what the PIF.MTU and VIF.MTU 
fields tell you (in the most recent XCP snapshot this should have been fixed). 
You should still be able to use ifconfig to find the MTU.

Important is that you unplug and plug all VIFs and PIFs that are connected to a 
network after changing the network's MTU, otherwise nothing happens. Could you 
try this?

Cheers,
Rob

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-
> bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Gémes Géza
> Sent: 21 September 2010 06:00
> To: James Harper; xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-users] XCP ethernet jumbo frames????
> 
> 2010-09-21 00:27 keltezéssel, James Harper írta:
> >> Hi,
> >>
> >> I have an XCP 0.5 box running a few DomUs some of the DomU's data is
> >> stored at (clustered lvm volumes on) a Coraid etherdrive box which
> is
> >> connected via an Ethernet cable to a dedicated card of the XCP box,
> for
> >> which in the network config I' ve specified: MTU=9344: xe
> >> network-param-list uuid=.... gives:
> >> MTU ( RW): 9344
> >> on the DomUs if I leave the MTU at 1500 (default settings)
> everything
> >> works (slowly, but works). If I increase the MTU the aoe device
> appear
> >> as expected, but the data on it becomes inaccessible, even just
> trying
> >> to activate the lvm volume groups gives a bunch of IO errors at
> sector
> >> 0, and so on.
> >>
> >> Please tell me what I'm doing wrong. Are jumbo frames expected et
> all to
> >> work?
> >>
> >>
> > Does your network adapter really support jumbo frames?
> > Is the network adapter on a bridge? (I'm unsure if Dom0 does AoE or
> if the DomU's do)
> > Are all the bridge interfaces set to 9344 MTU?
> > Could tcp offload settings break any of this? (unlikely - AOE is not
> TCP)
> >
> > tcpdump might tell you what's going on.
> >
> > James
> >
> The network adapter seems to be ok.
> I've tried to do aoe at the DomU's.
> I've set the network bridge's MTU at the bridge which is connected with
> the Coraid box.
> 
> After some tcpdumping I've checked what the good old ifconfig would say
> about my interfaces. Surprisingly while xe network... reports MTU=9344
> ifconfig says it is at 1500 (the vifs attached to the bridge have 9344
> ), while xe pif... reports all interfaces to have MTU=1500 (I have an
> other interface set at MTU=4200, which shows itself even with ifconfig
> as having MTU=4200). I start to get really confused :-(
> 
> Cheers
> 
> Geza
> 
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