EPICS across subnets

[Randall Cayford via Tech-talk <tech-talk at aps.anl.gov>]

I’m trying to understand what the options are for working with EPICS across subnets and for remote access.

We have some IOCs running on subnet A.  We also need access to a few PVs from IOCs running on network B.  I would like to access PVs on both A and B from subnet C.  Subnets are separated by multiple layers of routers.  Subnet A is on the experimental floor and is pretty locked down to control network traffic. 

My understanding is that EPICS_CA_ADDR_LIST will let me access other subnets but only if if multicast packets are passed between the subnets or if there is a cagateway running.  Is that correct? 

If cagateway is running on subnet B does it pass only the packets requested by a client on subnet A or does it pass all the broadcast traffic from subnet B?

Is EPICS_CA_ADDR_LIST supposed to include all of subnet B (subnetB.255) or just the IP of the gateway?

What router access rules are needed to allow connections to PVs on B from clients on A or C?

Does PVaccess change any of this?


I’m sure this is all somewhere in the documentation but I haven’t been able to sort it out by reading.  This involves a lot of different people to set up so I’m looking for some clarity on what needs to be done and who needs to do it.

Randall