Experimental Physics and
Industrial Control System

Michael Davidsaver <[email protected]> · Mon, 31 Oct 2016 10:30:12 -0400

On 10/31/2016 07:09 AM, Benjamin Franksen wrote:
> Hi everyone,
> 
> we finally found out what caused this strange behaviour. There was
> indeed a misconfiguration in the network: a new device was mistakenly
> copnfigured to use the same IP address as the IOC. For reasons that
> remain mysterious to me this condition was/is not detected by our
> network administrators. Instead we found out by trial and error and a
> bit of luck: someone had the idea to unplug the IOC and then issue a
> ping (which was answered by the 'imposter'). If the new device had been
> configured to not answer pings we would still be wondering...

FYI, looking at the MAC in the arp cache of the client machine is a sure
way to detect this.

> Cheers
> Ben
> 
> On 05.08.2016 17:23, Benjamin Franksen wrote:
>> """
>> We have a PC with Windows 7 that has Labview and an EPICS base 3.14.12.2
>> installed. This PC connects to several channel access servers. The
>> servers that are Linux based, like a channel access gateway and a
>> softioc, make no problems. However, since last week, connections to a
>> vxWorks IOC are no longer possible.
>>
>> "cainfo" for a PV on this IOC replies something like "connection reset
>> by host", although the correct host is mentioned. So it seems that the
>> name resolution request for the PV works but the connection to actually
>> transmit the data is interrupted or can't be established at all. Both
>> systems are within the same network collision domain.
>>
>> A Linux channel access client in the same network has no problems with
>> it's connections to the same PVs, so it doesn't seem to be a server
>> related problem.
>>
>> Now, if we change the IP address on the windows PC to another free
>> address in the network, channel access first works. Everything is fine
>> but only for 3 to 5 minutes. Then connections to the vxWorks IOC fail
>> again. Setting the IP address to a third variant has the same effect.
>> Everything works but only for a few minutes. Setting the IP address back
>> to the original one still doesn't work. Deactivating and  re-activating
>> the network interface doesn't help. After a while, maybe  15 to 30
>> minutes, an IP address that didn't work and wasn't used for that time,
>> can be used again, but still, only for 2 to 3 minutes.
>>
>> Setting EPICS_CA_ADDR_LIST to the IP of the IOC and
>> EPICS_CA_AUTO_ADDR_LIST to "no" doesn't help. But channel access on the
>> windows PC is not completely broken. Requesting PVs from our linux
>> based channel access gateway or a linux soft-IOC always works.
>> """

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System