NAT Virtual Interface

This article is important, for having a good understanding of NAT.

I do understand that the real issue is : How to reach a WAN address from a LAN domain, by pinging a LAN address (that is supposed to be translated to the target WAN address). I do also understand that the solution is not supposed to use routing rules for jumping from LAN side to WAN side.

However, some points are confusing for me.

  • Point-1

The issue is first demonstrated by typing the command below :

R1#ping 192.168.12.3 repeat 1

But ; the following explanation lines do no longer use it. Instead, the command below is always used (until the begining of the section “NAT Virtual Interface”) :

R3#ping 192.168.23.1 repeat 1

  • Point-2

Hard to see (in the debug ouptut) the difference between using “add-route” or not-using “add-route” !

  • Point-3

The text below lets suppose that it takes two “ip nat source static” commands for the configuration of NVI.

Now let’s convert our old two NAT commands into new NAT commands:
R2(config)#ip nat source static 192.168.12.1 192.168.23.1
R2(config)#ip nat source static 192.168.23.3 192.168.12.3

  • Point-4

In the command below :

R2(config)#interface range GigabitEthernet 0/1 - 1

I would say “2” at the place of the last “1”

  • Point-5

The first NVI configuration example (Static NAT) does not show that the initial issue has been solved. Again, why do the command below is not tried again ?

R1#ping 192.168.12.3 repeat 1