What are the ip addresses of a GRE keep alive packet

[historicalswimming]

What are the ip addresses of a GRE keep alive packet?

I am referring to  the internal and external IP headers

[MHM Cisco World]

I run small lab and you can see the outer and inner, 
the inner is intersting, it show the tunnel source and destiantion but reverse. 
anyway hope this naswer you.

[historicalswimming]

is 4.4.4.4 and 1.1.1.1 the   tunnel source and destination ip?

[MHM Cisco World]

Yes in my lab 
I use in one peer
interface tunnel 0
ip address 5.0.0.x
tunnel source 1.1.1.1
tunnel destination 4.4.4.4