With GNS3, you can simply see NAT functioning by configuring a nat setup between two connected routers. The transport is your choice but I used FastEthernet for simplicity.
R0 - NAT router
int loop1
ip add 10.0.0.1 255.255.255.0
ip nat in
!
int f0/0
ip add 192.168.0.1 255.255.255.252
ip nat out
!
access-list 1 per host 10.0.0.1
ip nat inside source list 1 interface f0/0 over
end
****************
R1
Configure FastEthernet interface
int f0/0
ip add 192.168.0.2 255.255.255.252
****************
Do a source ping from the loopback on the NAT router to the IP on R1 and view nat statistics and translations to see the attempt. Here is the output:
Router#ping 192.168.0.2 source 10.0.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.2, timeout is 2 seconds:
Packet sent with a source address of 10.0.0.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/8/12 ms
Router#sh ip nat stat
Total active translations: 1 (0 static, 1 dynamic; 1 extended)
Outside interfaces:
FastEthernet0/0
Inside interfaces:
Loopback1
Hits: 9 Misses: 1
Expired translations: 0
Dynamic mappings:
-- Inside Source
[Id: 1] access-list 1 interface FastEthernet0/0 refcount 1
Router#sh ip nat trans
Pro Inside global Inside local Outside local Outside global
icmp 192.168.0.1:0 10.0.0.1:0 192.168.0.2:0 192.168.0.2:0
You can do several scenarios and this is certainly not the only way to do it. However it will get you started and takes about <5 mins to set up.
Cheers
