Understanding EPICS_CA_ADDR_LIST and caget

[Sean Leavey via Tech-talk <tech-talk at aps.anl.gov>]

Hi tech talkers,

I don't seem to be able to change the behaviour of caget using 
EPICS_CA_ADDR_LIST. I'm probably misunderstanding something.
I've got EPICS Base installed on my machine. In one terminal I've got 
tcpdump monitoring port 5064. In another terminal I run caget with a 
made-up channel. Here's their output after I run caget:
$ caget FAKE:CHANNEL
Channel connect timed out: 'FAKE:FAKE' not found.

$ tcpdump port 5064
tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on wlan0, link-type EN10MB (Ethernet), snapshot length 262144 
bytes
09:11:07.345310 IP totoro.41026 > 172.16.15.255.ca-1: UDP, length 48
09:11:07.377158 IP totoro.41026 > 172.16.15.255.ca-1: UDP, length 48
09:11:07.441438 IP totoro.41026 > 172.16.15.255.ca-1: UDP, length 48
09:11:07.569269 IP totoro.41026 > 172.16.15.255.ca-1: UDP, length 48
09:11:07.825253 IP totoro.41026 > 172.16.15.255.ca-1: UDP, length 48

So far, so good? Looks like caget is sending 5 broadcast packets then 
giving up. 172.16.15.255 is my link's broadcast address, verified with 
`ip addr`.
But what if I know the IP of the IOC that hosts a channel, and want to 
specify it directly? I read in [1]:
> To reach IOCs on one or more additional subnets, the environment 
variable EPICS_CA_ADDR_LIST needs to be configured. It can list either 
the specific IP addresses of each IOC, or the broadcast address of their 
subnet. Note, however, that routers will often not forward broadcast 
requests, which suggests using specific IP addresses.
This sounds useful to me because my IOC is in a different subnet. From 
the quoted text above, I understand that, by setting EPICS_CA_ADDR_LIST 
to the IP of my IOC, caget should talk directly to it. But apparently 
this is not the case. Keeping tcpdump open, and running the caget 
command again but this time with the address of my IOC set in 
EPICS_CA_ADDR_LIST, I get the same output:
$ EPICS_CA_ADDR_LIST=195.194.120.115 caget FAKE:FAKE
Channel connect timed out: 'FAKE:FAKE' not found.

$ tcpdump port 5064
[...]
09:14:18.995465 IP totoro.35942 > 172.16.15.255.ca-1: UDP, length 48
09:14:19.027341 IP totoro.35942 > 172.16.15.255.ca-1: UDP, length 48
09:14:19.091486 IP totoro.35942 > 172.16.15.255.ca-1: UDP, length 48
09:14:19.219462 IP totoro.35942 > 172.16.15.255.ca-1: UDP, length 48
09:14:19.475597 IP totoro.35942 > 172.16.15.255.ca-1: UDP, length 48

Clearly I'm misunderstanding how all of this works. Can someone shed 
some light on what EPICS_CA_ADDR_LIST does in the context of caget, if 
anything?
Cheers,
Sean

[1] 
https://epics-controls.org/resources-and-support/documents/howto-documents/configure-channel-access/#IOCs_on_different_subnets
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