Hi Hammad,
The "nopreservation" keyword enables all the IP addresses in the pool to be used for dynamic translation.
Comparisons with option turned on and off:
===================================
a) option on:
ip nat pool test 10.0.0.1 10.0.0.2 prefix-length 24 nopreservation
c1841-7#sh ip nat tr
Pro Inside global Inside local Outside local Outside global
53 10.0.0.2:0 25.1.1.13:0 14.1.1.11:0 14.1.1.11:0
--- 10.0.0.2 25.1.1.13 --- ---
53 10.0.0.1:0 25.1.1.14:0 14.1.1.11:0 14.1.1.11:0
--- 10.0.0.1 25.1.1.14 --- ---
The above shows that the first nat pool address is available for nat translation.
Or:
c1841-7#sh ip nat tr
Pro Inside global Inside local Outside local Outside global
udp 10.0.0.2:6300 25.1.1.13:6300 14.1.1.11:6300 14.1.1.11:6300
53 10.0.0.1:0 25.1.1.14:0 14.1.1.11:0 14.1.1.11:0
--- 10.0.0.1 25.1.1.14 --- ---
The above shows that the first nat pool address is available for nat translation.
a) option off:
ip nat pool test 10.0.0.1 10.0.0.2 prefix-length 24
c1841-7#sh ip nat tr
Pro Inside global Inside local Outside local Outside global
udp 10.0.0.2:6300 25.1.1.13:6300 14.1.1.11:6300 14.1.1.11:6300
The above shows that the first nat pool address is not available for nat translation of packets with ip unknown protocols.
Please let me know if this information helps you.
Regards,
Bernardo
