[ovs-discuss] Best practice trouble-shooting

[Luiz Ozaki]

On 3/14/12 2:03 PM, Mike Bursell wrote:
> Hi -
>
> One useful piece of work that we're thinking of doing and then sharing with the community is a trouble-shooting guide, aimed more at sysadmins and support engineers than developers.  So, I thought I'd ask here to find out:
>
> 1) what behaviours do you look for that suggest there are problems with normal operation?
> 2) what documentation do you find most/least useful?
> 3) how do you navigate the logs, and what's most/least useful there?
> 4) what tests do you tend to try in order to trouble-shoot problems.
>
> Although I'm hoping I'll get replies from everyone's good friends at Nicira, I'm particularly interested to hear from people using OVS in the field.
>
> TIA,
>
> -Mike.
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*Show the bridge/vifs connections*
brctl show

*vSwitch overhead diagnostic:*
ovs-dpctl show
@lookups lines:
   - lost numbers should not increase, getting this counter up means 
high latency/drop packets
   - missed packet went to userland - okayish
   - hit is the optimal, packet went only in kernelspace - Best case

*Inspect packets:*
eth# ---- xapi# ---- vif##.0
tcpdump on each part of the schema to diagnose where the problem is. Eg.:
tcpdump on the eth shows if the packets is passing from/to physical network
tcpdump vif##.0 shows the packets from/to VM

So, if the packet is passing throught eth and it's not getting into the 
VM destination vif, probably the packet is being droped or not forwarded 
by the OVS
Same goes for output packets from the VM. It's passing throught the vif, 
but it's not getting into the eth.

*Shows current flows:*
ovs-dpctl dump-flows <bridge>

*Show installed flows:*
ovs-ofctl dump-flows <bridge>

*Trace openflow:*
ovs-appctl ofproto/trace
(I simulated some packets looking at the [openvswitch] 
<http://openvswitch.org/cgi-bin/gitweb.cgi?p=openvswitch;a=tree;hb=HEAD>/tests 
<http://openvswitch.org/cgi-bin/gitweb.cgi?p=openvswitch;a=tree;f=tests;hb=HEAD>/ofproto-dpif.at 
<http://openvswitch.org/cgi-bin/gitweb.cgi?p=openvswitch;a=blob_plain;f=tests/ofproto-dpif.at;hb=HEAD> 
in the OVS source code and changing accordly to my needs)

*MAC table*
ovs-appctl fdb/show <bridge>

*Show bond configuration*
ovs-appctl bond/show <bond>


Some sort of quick reference that I had in mind to diagnose some OVS 
problems. At least when implementing openflows using OVS.

-- 
Luiz Henrique Ozaki

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