BTW, just tried some tunnel config "stuff" in Packet Tracer (which cannot be counted on to be accurate on "real" Cisco platforms, but some it's accurate, so . . .).
The moment I configured a tunnel interface, tunnel interface appeared with status of up/down.
To get the tunnel to change status to up/up, had to insure 4 things.
Source interface that's up/up, with an IP address.
Tunnel interface with source defined (the aforementioned source interface).
Tunnel interface with any destination IP defined BUT router KNOWs and has a next hop for destination.
E.g.
conf t
Would you like to enter the initial configuration dialog? [yes/no]: n
Press RETURN to get started!
Router>en
Router#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#int g0/0/0
Router(config-if)#ip address 1.1.1.1 255.255.255.0
Router(config-if)#no shut
Router(config-if)#
%LINK-5-CHANGED: Interface GigabitEthernet0/0/0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0/0, changed state to up
int g0/0/0
Router(config-if)#ip address 1.1.1.1 255.255.255.0
Router(config-if)#no shut
Router(config-if)#int t1
Router(config-if)#tunnel source g0/0/0
Router(config-if)#tunnel destination 1.1.1.2
Router(config-if)#
%LINK-5-CHANGED: Interface Tunnel1, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface Tunnel1, changed state to up
