Disconnected link to server node is still able to be accessed/clicked on to run effects.
There has been only one reported case of this; however, a disconnected server node link to an "island server node" allowed SECURE to be run on that server node.
I believe that if a server node has been disconnected or isloated from the rest of the network that it should not allow the player to click on it to run DCO/CND effects. If that player is adjacent to that server node then they will be allowed to reacquire that server node.