Re: [vserver] transient network drops

I spent some quality time with my smart switch, and found out the culprit:

  85.10.225.64 00e081-5858b2 dynamic
  85.10.225.64 00e081-5858b3 dynamic 7

strange, eh? Given

 eth0 Link encap:Ethernet HWaddr 00:E0:81:58:58:B3
 eth1 Link encap:Ethernet HWaddr 00:E0:81:58:58:B2

we have a case of the MAC flipping from one interface in
the other. Whether this only happens to vservers, or
vservers with lots of traffic, or also the physical
server NIC is to be determined.

I've heard that some SunFire X2100 were known to let
the MAC move over to another NIC, which might be the case
here.

On Thu, Aug 30, 2007 at 10:27:16AM +0200, Eugen Leitl wrote:
>
> I'm running some 13 vservers on a SunFire X2100 with two
> NICs, using 2.6.15-amd64-smp-vs on AMD64 debian sarge.
>
> Ethernet interfaces:
>
> eth0: Tigon3 [partno(BCM95721) rev 4101 PHY(5750)] (PCI Express) 10/100/1000BaseT Ethernet 00:e0:81:58:58:b3
> eth0: RXcsums[1] LinkChgREG[0] MIirq[0] ASF[1] Split[0] WireSpeed[1] TSOcap[1]
> eth0: dma_rwctrl[76180000]
>
> eth1: forcedeth.c: subsystem: 0108e:5348 bound to 0000:00:0a.0
>
> eth0 is the main system interface with an MTU of 1500, eth1
> used on a local interface with a MTU of 9000.
>
> I have semiregular sporadic outages on one vserver (xxx.xxx.xxx.64 on
> a /24 network), which last many minutes, and resolve spontaneously.
> They resolve immediately if the vserver is restarted, and they also
> resolve immediately if I remove the entire machine from the network
> by disabling the port on the gateway switch (but typically reappear
> soon after).
>
> The source of the outages for that guest is definitely located in
> the host (I can ping that server just fine from the host during
> outages though, and ditto from other machines on the same switch (all
> those are also connected via eth1 to a private network).
> I've verified this by running MTR (there's a firewall in front
> of the machine which is in transparent bridge mode which I suspected
> first, but bypassing it made absolutely no difference).
>
> >From the symptoms it looks like ARP or MAC (as a wild-ass guess,
> I've heard that some SunFire X2100 models MACs can move across
> different NICs) trouble. How can I diagnose this to narrow this
> further down?

-- 
Eugen* Leitl leitl http://leitl.org
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