Hello,
With NAT, the original IP header is not saved. With static NAT you are using, the ip nat commands build the entire translation table that describes the correspondence between internal and external addresses and how the IP header is modified when passign through a NATting device:
- For traffic going from inside to outside, the source address is rewritten from inside local to inside global address
- For traffic going from outside to inside, the destination address is rewritten from inside global to inside local address
Note please that this principle does not need any storage of "original" IP header. Simply matching for the appropriate IP address in the IP header and its rewriting according to the translation table is what the static NAT does in your case.
What problem are you experiencing?
Best regards,
Peter
