"ip address"/"ip unnumbered" for Tunnel interface

m4rtin

I have a following tunnel interface configuration:

C1841#sh run int tu0
Building configuration...

Current configuration : 153 bytes
!
interface Tunnel0
 ip address 8.8.8.8 255.255.255.0
 keepalive 5 3
 tunnel source FastEthernet0/0
 tunnel destination 10.10.10.1
 tunnel checksum
end

C1841#

Am I correct that IP address 8.8.8.8 is used as a source IP address in the GRE encapsulated IP header only in case the packet is originated from the C1841 router itself?

creamy_stew

I would assume so (unless you're doing NAT/PAT of course)

How does ip unnumbered enter into this?