Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Tue, 06 Nov 2001 10:27:15 -0600

Vladis Korobov wrote:
> 
>    If CA clients (for example, MEDM screen) connected before the second
> interface was attached all is OK. I can get and put PVs from MEDM screen.
> But if I close this screen and then try to open it again after "ei" interface
> already attached, I can't access anymore the PVs. The same for the telnet
> connection to the slave and 'caget' and 'caput' requests.

It sounds like the plc network has offerred a "better" TCP/IP route than
the sm one, so further connections may be going via the wrong port.  Use
routeShow before and after starting the second network and see what
routing changes occur.

>    Is it possible anyhow to coexist for both of these interfaces and not to
> interfere with each other: for CA connections to go always via "sm" interface
> and for the PLC's ones only via "ei" interface? Or this is impossible,
> and the last attached interface becomes the master?

It should be, but you may have to reorder your startup slightly.  Jeff
Hill will no doubt confirm or contradict this, but I think you may have to
start the second network interface before iocInit - there's no way of
telling the Channel Access server that a new network interface is present,
and I think it may need to know (although that may not be true if you'll
only ever use that subnet for PLC communications, never CA.  In that case
I suspect your problem is routing, maybe you're not setting the subnet
mask for the new interface properly?).

You should probably experiment with setting the EPICS_CA_ADDR_LIST
environment variable in this configuration too - we found that EPICS
running on the Master IOC was generating duplicate beacons (which shows up
as excess network traffic and nameserver usage but doesn't stop anything
working) and have to set EPICS_CA_AUTO_ADDR_LIST=NO and explicitely set
EPICS_CA_ADDR_LIST to get it to work properly.

In your case you'll probably need the Master's EPICS_CA_ADDR_LIST set to
the broadcast address of the main network segment plus the IP address of
the Slave IOC.  On the slave you can stop CA from broadcasting to the PLC
network by setting EPICS_CA_ADDR_LIST to the broadcast address of the sm
network (or should that be the broadcast of the main network, I'm not sure
- Jeff?).

- Andrew
-- 
Perfection is reached, not when there is no longer anything to add,
but when there is no longer anything to take away.
- Antoine de Saint-Exupery

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System