[Bridge] Re: No UDP NFS over bridges in Linux 2.6.16.x?

Stephen Hemminger shemminger at osdl.org
Fri Apr 14 13:53:21 PDT 2006


On Fri, 14 Apr 2006 20:26:56 +0100 (BST)
Chris Rankin <rankincj at yahoo.com> wrote:

> --- Stephen Hemminger <shemminger at osdl.org> wrote:
> > Most likely the problem is that the MTU on the two devices in the bridge is different.
> > The bridge will silently drop packets if they are too large for the destination port (it's in
> > the 802.1d standard). TCP has path mtu discovery and is smart enough to recover.  UDP doesn't do
> > that.
> 
> Hi,
> 
> Thanks for the top about the dangers of NFS and UDP. However, I don't think that the MTU is the
> problem. All the ethernet devices (including the bridge) have an MTU of 1500, and according to my
> routing table, only the default route has a lower MTU. Both servers are configured like this:
> 
> 192.168.0.0/24 dev eth0  proto kernel  scope link  src 192.168.0.x
> 169.254.0.0/16 dev eth0  scope link
> default via 192.168.0.1 dev eth0  src 192.168.0.x  advmss 1452
> 
> eth0      Link encap:Ethernet  HWaddr nn:nn:nn:nn:nn:nn
>           inet addr:192.168.0.x  Bcast:192.168.0.255  Mask:255.255.255.0
>           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>           RX packets:6817 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:4951 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:1000
>           RX bytes:1840267 (1.7 MiB)  TX bytes:678873 (662.9 KiB)
>           Base address:0xdcc0 Memory:ff6e0000-ff700000
> 
> So all traffic between 192.168.0.x machines should be routed with an MTU of 1500.
> 
> Cheers,
> Chris

What is the mtu of eth0 and eth1 on the bridge?

> 
> 
> 
> 		
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-- 
Stephen Hemminger <shemminger at osdl.org>
OSDL http://developer.osdl.org/~shemminger



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