npath dsr configuration ltm 11.x

Hi Could anyone please confirm source IP of the IPIP tunnel between F5 and server...

I did verification of L3 DSR (for SIP,DHCP/UDP) using virtual edition 11.3 and couldn't get LB to source the tunnel from it's IP - it always used client IP as a source of the tunnel (unless SNAT was enabled but then both tunnel and client IPs are changed).

I cannot get my server ('black box') to accept IPIP tunnel from anywhere. Is there a way to force F5 to use it's IP as source of IP (or GRE) tunnel in npath l3?

Thank you for your time /Zeljko