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<== Date ==> <== Thread ==>

Subject: RE: Multiple Network quesion
From: "Jeff Hill" <johill@lanl.gov>
To: "'Andrew Johnson'" <anj@aps.anl.gov>
Cc: "'Adam DeGrush'" <degrush@mit.edu>, <tech-talk@aps.anl.gov>
Date: Mon, 19 May 2003 20:13:32 -0600
> You *do* see them if both the IOC and the CA client are running
> on the same machine - my Linux Laptop has both a wireless and 
> a wired network interface, and when both are active I have to
> set EPICS_CA_ADDR_LIST to one network address and turn off
> AUTO_ADDR_LIST to stop the errors.

Yes. If you have two or more LAN type network interfaces
(interfaces supporting broadcasting), and the client and server
are on the same host broadcasting out all of the local
interfaces, then you would probably see those messages. 

The trouble is that there could be perfectly valid situations
where there are two servers on the same host each bound to a
nonintersecting set of network interfaces with
EPICS_CAS_INTERFACE_ADDR_LIST. In that situation the warning
messages sent to local clients broadcasting out all of the local
interfaces would be perfectly valid, and perhaps someone would
complain if they didn't receive them. Admittedly that is surely a
less common configuration. 

> 
> This situation is something which might be fixable inside CA -
> could you check if the duplicate addresses are both interfaces
> on this machine and silently ignore duplication?

This could be done with some overhead. I would need to check to
see if the duplicate was from a list of directly attached
interfaces and then check to see if the first response was also
from among that list of interfaces. But again, lacking knowledge
the server's configuration, suppression of the messages wouldn't
be valid in all situations.

PS:

If EPICS_CA_AUTO_ADDR_LIST is YES then the client library builds
a list of search addresses from the interfaces that are
installed. In R3.14 duplicate entries resulting from the
interface query are silently removed. I have tested on a host
where there were two network interfaces on the same subnet and
the client and server were on the same host, but in that
situation the duplicate entries were silently removed.

Jeff


> -----Original Message-----
> From: Andrew Johnson [mailto:anj@aps.anl.gov]
> Sent: Monday, May 19, 2003 1:16 PM
> To: Jeff Hill
> Cc: 'Adam DeGrush'; tech-talk@aps.anl.gov
> Subject: Re: Multiple Network quesion
> 
> Jeff Hill wrote:
> >
> > If you have the common situation where your host has multiple
> > network interfaces each attached to a different IP subnet
> > (broadcast domain), then you will *not* see these messages.
> 
> You *do* see them if both the IOC and the CA client are running
> on the
> same machine - my Linux Laptop has both a wireless and a wired
> network
> interface, and when both are active I have to set
> EPICS_CA_ADDR_LIST to
> one network address and turn off AUTO_ADDR_LIST to stop the
> errors.
> 
> This situation is something which might be fixable inside CA -
> could you
> check if the duplicate addresses are both interfaces on this
> machine and
> silently ignore duplication?
> 
> - Andrew
> --
> There are 10 types of people in the world:
> Those who understand binary, and those who don't.



References:
Re: Multiple Network quesion Andrew Johnson

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