Experimental Physics and
Industrial Control System

Chris Timossi <[email protected]> · Thu, 14 Jul 2005 15:22:10 -0700

Thanks everyone. It sounds like the ca gateway will almost work my
purpose (1 NIC, dedicated subnet). The only wrinkle is that we'd like
the gateway to receive beacons so we need to add the gateway's broadcast
or ip address to the IOC's EPICS_CAS_BEACON_ADDR_LIST; unfortunately
this option is only available in R3.14.
Chris
Ralph Lange wrote:
Hmmm....
There is an environment variable (affecting the server side of the
Gateway) to mask out single IP addresses so that the Gateway will just
ignore name resolution requests from those addresses. That is normally
used to prevent loops in a multi-Gateway environment by making
Gateways ignore requests from other Gateways.
For the client-side configuration it's either complete subnets or
single IP numbers, correct.
I'm not sure if this will work on a single NIC machine, though. You
might be running into a situation, where the Gateway (on its server
side) while being perfectly configured for a -sip in network A still
sees name resolution requests coming form network B since it uses the
same NIC. For that case I'm not sure what has to be configured in
which way.
For Chris' original description - wasn't the Gateway sitting on a
third, separate network anyway? So that clients that want to see the
Gateway have to add its IP explicitly to their EPICS_CA_ADDR_LIST
anyway? In that case I don't see that there should be a problem for
clients on the IOC side network (e.g. the IOCs themselves), as they
also would have to explicitly add the Gateway IP to EPICS_CA_ADDR_LIST
to have their name resolution requests directed to it. Broadcast
requests from clients (empty EPICS_CA_ADDR_LIST) will usually stay
within the network. (Only advanced switch/router configuration can
change this.)
Cheers,
Ralph

Dayle Kotturi wrote:
Hi Chris,
I have some experience with this. A single host with dual-NICs needed to

act as a CA gateway server in two directions. In order to prevent the

ambiguity you suggest, it was necessary to explicitly lists the
sources of

PVs (since there is no way to mask out an IP addr) for each CA gateway

process AND to make sure the CA gateway process ran as the correct IP

(that's the -sip arg or the EPICS_CAS_INTF_ADDR_LIST env var). Note that

wildcards wouldn't work in my case, since if I used them, I'd be
including

the server and creating ambiguity.
HTH,

Dayle Kotturi
[email protected]

LINAC Coherent Light Source

Stanford Linear Accelerator Center

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System