I have a caseta pro hub. I can telnet to it just fine, and the Lutron app on my phone controls things just fine.
But, Hubitat does not work with it. The caseta hub is on a separate subnet. Could this be a problem? The Hubitat is on a subnet that has full access to the subnet that the Caseta hub is on, and port 23 is open. I'm not seeing any errors.
Are you using the default Lutron username and password on the Caseta SmartBridge Pro? I can't recall if Caseta allows the Telnet username/password to be changed or not?
If so, it needs to be
Username: lutron
Password: integration
Is your Lutron Hub using a DHCP address or a Static IP? Is it's Gateway address set correctly?
When you are using Telnet, are you trying from the same vlan that the Hubitat hub is connected to?
Static address. I don't see any way to edit creds. Isn't that only for the Radio RA2 stuff?
And yes, I am testing from a laptop on the same vlan the Hubitat is on. The Hubitat is talking to other things on the other vlan just fine.
Yes, that sounds correct.
What happens if you move the Lutron hub to the same vlan as the Hubitat hub, or vice versa? Just to see if that truly is the problem?
I haven't tried it yet. I will try it in a bit. I wanted to avoid that because if it works it will never go back. 
Plus, I don't remember what port it's in and I have been too busy today to go and look so I can change the vlan on the right port.
or allow the hubitat hub to communicate to the lutron bridge between vlans 
It is allowed.
Finally got around to moving it to the same subnet. It works now. I'd prefer if I could move it back to the other subnet though.
Also, could it be possible in the future to just upload the json and select the devices that I want to create and their types? As opposed to manually perusing the json and creating a csv manually.
Someone posted a tool or script that does the translation. Maybe search for it.
Hmm, looks like it might not just use port 23 for control. 22, 8081, and 8083 are open. Guessing that it also requires at least one of those ports to be allowed in the firewall rule. Since the Lutron app is a built in one, I can't look at the code to see how it's communicating.
Can someone from Hubitat take a quick look at the code and tell me what ports it communicates over?
It is standard Telnet, so port 23.
Is that the only port that it uses though? The caseta hub listens on those 4 ports that I listed above.
Yes. When I had my Hubitat and Caseta Pro bridge on separate VLANs, TCP port 23 was the only port that was opened on the VLAN with the Caseta Pro bridge.
The caseta bridge also communicates with the Lutron cloud and HomeKit.
So why didn't mine work on separate vlans? Port 23/tcp was open from the one with the Hubitat to the on with the caseta hub.
23 has to be open on the one with the Lutron bridge.
(The source port from HE can be any non-privileged port number …)
What I am saying is that the Lutron bridge listens on 23, but also on those other ports. It makes me think that the communication to the Hubitat is not just over 23.
I only had opened 23 to the Lutron hub in my firewall. I wonder if I had opened the other ones if it would have worked.
Hubitat only uses Telnet (port 23) to communicate with the
Lutron bridge. Make sure you allow traffic FROM the Hubitat hub to initiate communication with the Lutron bridge on port 23.
This is what I also believe the issue is. Make sure that you permit all source traffic from the Hubitat. Which, will only use non-privileged ports (so 1025-65535).
Download the Hubitat app
