Gre can not use loopback virtual IP

[stegbth]

hi,

i set up a IPsec/GRE tunnel with two PFsense 2.2.3.
One side has an dynamic ip on WAN.

So i thought about creating an IP Alias on loopback create an IPsec tunnel with tunnel mode (instead of transport) and use the loopback IP as GRE tunnel source.

Unfortunatly the gre tunnel get created, but there are no source/destination IP's defined. only the interface IP and remote IP are setup.

I was able to solve the problem with NAT router doing the dialin and provides an internal ethernet.

Made i something wrong or is this simply not possible to use an loopback as tunnelsource?

greets
Thomas