Thunderbolt does not work on High Sierra iMac 27 mid 2011

viorel275 wrote:

with all due respect , my question was , still is , how to enable my TB port

Your description of your dock is far too vague.

"an old powered dock - on one end of the cable is a "plug" not dissimilar with Thunderbolt plug , on the other an ordinary USB plug , two black cables and one blue , all told ; they seem to have the same terminal plugs ( I suspect it is USB 2 ) -

and then you mention

"these cables < For Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter A1790 + TB2 2M Cable >"

So one question is whether the dock is a Thunderbolt dock, that is connected by Thunderbolt to one of the Mac's old-style Thunderbolt 1 ports. The cables you mention would only come into play if you were trying to connect a Thunderbolt 3 dock to an old Mac (like yours) with Thunderbolt 1 or 2. If the dock is a Thunderbolt 1 or 2 one you would not need the adapter, and if was a Thunderbolt 4 or 5 one, the standards might not support using it with an old Thunderbolt 1 or 2 equipped computer even with the adapter.

You also mentioned an unpowered USB hub. Such a hub could not help you attach anything via Thunderbolt.

on system preferences >> network >> Thunderbolt is on red

Network Preferences is for networking. Since you are not trying to network two Macs, using a Thunderbolt link as if it was an Ethernet link, I would expect the Thunderbolt network interface to be down ("on red") all of the time.

It may be possible to make a bootable external drive but your TB ports are slow compared to new thunderbolt ports. Your Mac is also very old by today's standards so you may want to look at getting a newer Mac. The easiest method would be to use a compatible version of Carbon Copy Cloner and clone your internal drive to an external SSD. This will be low cost but like Im stated I would consider upgrading to a newer unit.

An iMac (27-inch, Mid 2011) would have both USB 2.0 ports and a faster FireWire 800 port.

I used a FireWire 800 SSD with a Late 2009 Mac – back when bus-powered notebook drive enclosures which had support for FireWire 800 and USB 3.0 were still available. Performance was acceptable relative to a hard disk, but the FireWire 800 interface limited the speed, and the setup did not deliver the sort of massive speed increase that one normally associates with SSDs.

viorel275 wrote:

I would like to boot from external SSD via Thunderbolt

Sounds like you would be unwilling to pay what it would cost to get a Thunderbolt enclosure for a SSD, even if you could find such an enclosure. Thunderbolt 1 and 2 enclosures tended to go hand in hand with RAIDs. Surprisingly, you can still get Thunderbolt 2 enclosures from OWC – although the cheapest one costs $229.99 without drives or 2.5"-to-3.5" mounting bracket adapters.

Other World Computing – Thunderbolt 2 Drives

So what are you hoping to get out of that old Thunderbolt dock – if it is a Thunderbolt dock? USB 3?

even so via USB it is acceptable fast for me , designing boats involves thinking first and only after introducing figures to calculate

If USB 2 is acceptably fast for you, maybe let sleeping dogs lie?

Sorry but not sure what you want to do with the TB port in the network pane. perhaps this discussion will help:

How to configure Thunderbolt Ethernet Gig… - Apple Community