if anyone knows about creating a tunnel between mikrotik box that one of the box behind NAT router please help me and point me in the right direction

Regards

You have to configure the nat-router to pass the tunneling-packets
through.
Here is how packets of ipip looks like:
http://www.ietf.org/rfc/rfc2003.txt?number=2003

If there is only one ipip tunnelling device behind nat you simple
pass all Pakets with protocol=4 to the MT box behind NAT.
The other MT uses the NAT-Address as peer.

Regards,
Stefan

If there is only one ipip tunnelling device behind nat you simple
pass all Pakets with protocol=4 to the MT box behind NAT.
The other MT uses the NAT-Address as peer.

Sorry to bump this up but when you say pass all Pakets with protocol=4, do you mean that we simply port forward TCP port #4 to the local private IP address?
Is that sample code good for a CISCO router?