Hi,
If you are using ASA 8.2 or before releases.... then you need to do configure like this.
access-list nonat extended permit ip 172.31.20.0 255.255.255.0 172.16.54.0 255.255.255.0
nat (inside) 0 access-list nonat
!
sameway if the 172.16.54.0 subnet is on another site, which is behing a FW... then in that firewall also they should do the nonat , required in case of site to site
access-list nonat extended permit ip 172.16.54.0 255.255.255.0 172.31.20.0 255.255.255.0
nat (inside) 0 access-list nonat
!
If you are running 8.3 + version of ASA OS, then here you get
object network lan
subnet 172.31.20.0 255.255.255.0
object lan destination
172.16.54.0 255.255.255.0
!
nat (inside,outside) source static lan lan destination static destination destination no-proxy-arp
!
on the other site.
object network destination
subnet 172.31.20.0 255.255.255.0
object lan lan
172.16.54.0 255.255.255.0
!
nat (inside,outside) source static lan lan destination static destination destination no-proxy-arp
Regards
Karthik
