telnet login delay

Telnet should work without the need for any particular configuration.

Hosts file is identical, resolv-conf are identical as well.

Have they been altered from their factory configuration? If so, for what purpose, and in what manner?

The Hosts file should be identical to the following, unless you had reason to alter it:

##

# Host Database

#

# localhost is used to configure the loopback interface

# when the system is booting. Do not change this entry.

##

127.0.0.1 localhost

255.255.255.255 broadcasthost

::1 localhost

There may be one additional entry if you are using IPv6 compliant devices:

fe80::1%lo0 localhost

resolv-conf normally contains only one line pointing to your DNS nameserver, which can be the address of your router assuming it receives its DNS entries supplied by your ISP. It should be inconsequential unless the telnet address needs to be resolved, and you wrote you're supplying it directly.

Did you contact Lutron? Perhaps they can offer something more constructive. Their engineers are pretty good, but don't let them shoot you down if they say they don't support Macs. Perhaps you shouldn't even offer that information. There is absolutely nothing Mac-specific about Telnet. There may be something on your Mac preventing it from working though, which would be beyond anyone's knowledge or control but yours.

Can I compare directories on the two machines ?

Sure, but they should be functionally identical to the above examples. Let me know what you find out.

Edit to add: if you are using any non-Apple "anti-virus" junk, don't. That just goes without saying.

Is there a particular port you might need to add to the Telnet command? Some devices will actively refuse a connection unless you specify that port (or perhaps it will time out, as you're experiencing).

Perhaps it's listening for input prior to issuing the login prompt? Try a carriage return or something like that.

Please let me know what Lutron says. I have homes full of their products. They're good.

Thanks for the update.

I don't know how an "older" Mac would affect telnet. It's pretty simple. The only suggestion I have would be to boot "Safe Mode" and determine if telnet works without a delay. If it does it might be worth pursuing a cause.