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

Subject: RE: Multihomed IOC
From: "Jeff Hill" <[email protected]>
To: "'Emmanuel Mayssat'" <[email protected]>
Cc: "EPICS-tech-talk" <[email protected]>
Date: Fri, 3 Nov 2006 15:19:57 -0700
PS: Currently, there are two commonly used approaches to simplifying
configuration of a multi-subnet EPICS system.

A) Use a multi-homed host running a CA gateway to provide transparent access
into a remote subnet.

B) Enable directed broadcast forwarding in the interconnecting routers while
at the same time configuring the directed broadcast address for the remote
subnet(s) into your client's address list.

Jeff

> -----Original Message-----
> From: Jeff Hill [mailto:[email protected]]
> Sent: Friday, November 03, 2006 9:38 AM
> To: 'Emmanuel Mayssat'; 'epics'
> Subject: RE: Multihomed IOC
> 
> 
> Emmanuel,
> 
> > I run an IOC on computer with 2 network interfaces.
> > When I try to caget a process variable I get an error telling me that
> > the PV is accessible from 2 addresses (multiple servers warning).
> 
> I could imagine seeing that result if you have configured your network
> interfaces to (both of them) be on the same subnet, and caget is being run
> on another host on this subnet?
> 
> Alternatively, if you are running caget on the same multi-homed host as
> the
> IOC then it might be necessary to explicitly configure the client's
> address
> list so that it does not broadcast on both subnets (and find the same IOC
> on
> both subnets)? And of course, you could just avoid running clients on
> machines that are also routers. In some situations maybe dedicated routers
> are cheap enough that we can avoid using workstations for this purpose?
> 
> > I tried to
> > EPICS_CA_AUTO_ADDR_LIST=NO
> > EPICS_CA_ADDR_LIST=<myHostname>:5064
> >
> > But then I get the message:
> > Empty PV search address list.
> > and cannot find the PV at all.
> 
> This (the empty search address list message) is not my experience here
> (testing on Linux). Admittedly I am not running on a multi-homed host, but
> I
> don't expect that would cause the address list to be empty when it is
> explicitly configured as follows.
> 
> ~$ export EPICS_CA_ADDR_LIST=wombat:5064
> ~$ export EPICS_CA_AUTO_ADDR_LIST=YES
> ~$ caget joh:fred
> joh:fred                       0.0066983
> 
> Jeff
> 
> > -----Original Message-----
> > From: Emmanuel Mayssat [mailto:[email protected]]
> > Sent: Thursday, November 02, 2006 7:53 PM
> > To: epics
> > Cc: [email protected]
> > Subject: Multihomed IOC
> >
> > Hello,
> > I run an IOC on computer with 2 network interfaces.
> > When I try to caget a process variable I get an error telling me that
> > the PV is accessible from 2 addresses (multiple servers warning).
> >
> > I tried to
> > EPICS_CA_AUTO_ADDR_LIST=NO
> > EPICS_CA_ADDR_LIST=<myHostname>:5064
> >
> > But then I get the message:
> > Empty PV search address list.
> > and cannot find the PV at all.
> >
> > It doesn't make any sense!
> > Please help,
> > --
> > Emmanuel


References:
RE: Multihomed IOC Jeff Hill

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