Below, there are some simple examples of NAT configurations on a Cisco router.
STATIC NAT:
interface fa0/0
ip address 10.1.1.2 255.255.255.0
ip nat outside
!
interface fa0/1
ip address 10.1.3.2 255.255.255.0
ip nat inside
!
ip nat inside source static 10.1.3.1 10.1.1.10
R3#show ip nat translations
Pro Inside global Inside local Outside local Outside global
--- 10.1.1.10 10.1.3.1 --- ---
host1#ping 10.1.1.10
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.1.10, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 ms
R3#show ip nat translations
Pro Inside global Inside local Outside local Outside global
icmp 10.1.1.10:5 10.1.3.1:5 10.1.1.1:5 10.1.1.1:5
--- 10.1.1.10 10.1.3.1 --- ---
PAT:
interface fa0/0
ip address 10.1.1.2 255.255.255.0
ip nat inside
!
interface fa0/1
ip address 10.1.3.2 255.255.255.0
ip nat outside
!
ip access-list extended NET_INSIDE
permit ip 10.1.1.0 0.0.0.255 any
!
ip nat inside source list NET_INSIDE interface fa0/1 overload
!
R3#show ip nat translations
Pro Inside global Inside local Outside local Outside global
icmp 10.1.3.2:6 10.1.1.1:6 10.1.3.1:6 10.1.3.1:6
NAT SRC & DST:
interface fa0/0
ip address 10.1.1.2 255.255.255.0
ip nat inside
!
interface fa0/1
ip address 10.1.3.2 255.255.255.0
ip nat outside
!
ip nat inside source static 10.1.1.1 10.1.3.10
ip nat outside source static 10.1.3.1 10.1.1.10
!
ip route 10.1.1.10 255.255.255.255 10.1.3.1
!
R3#show ip nat translations
Pro Inside global Inside local Outside local Outside global
--- --- --- 10.1.1.10 10.1.3.1
--- 10.1.3.10 10.1.1.1 --- ---
R3#show ip nat translations
Pro Inside global Inside local Outside local Outside global
--- --- --- 10.1.1.10 10.1.3.1
icmp 10.1.3.10:10 10.1.1.1:10 10.1.1.10:10 10.1.3.1:10
icmp 10.1.3.10:18 10.1.1.1:18 10.1.1.10:18 10.1.3.1:18
--- 10.1.3.10 10.1.1.1 --- ---
Dynamic NAT:
interface fa0/0
ip address 10.1.1.2 255.255.255.0
ip nat inside
!
interface fa0/1
ip address 10.1.3.2 255.255.255.0
ip nat outside
!
ip access-list extended NET_INSIDE
permit ip 10.1.1.0 0.0.0.255 any
!
ip nat pool NAT_OUTSIDE 10.1.3.1 10.1.3.254 prefix-length 24 type match-host
!!!!!!!!!!!!!!!!!!!!!!
! Alternative:
!ip nat pool NAT_OUTSIDE 10.1.3.9 10.1.3.254 prefix-length 24 type rotary
!!!!!!!!!!!!!!!!!!!!!!!!
!
ip nat inside source list NET_INSIDE pool NAT_OUTSIDE
R3#show ip nat translations
Pro Inside global Inside local Outside local Outside global
icmp 10.1.3.10:27 10.1.1.10:27 10.1.4.1:27 10.1.4.1:27
--- 10.1.3.10 10.1.1.10 --- ---
