Twice Nat Example; Figure 8: Twice Nat Example - Juniper JUNOSE 11.0.X IP SERVICES Configuration Manual

NOTE: Null route applies to 192.32.6.0 and 192.32.6.1, which do not exist in the
address pool.

Twice NAT Example

Twice NAT is often useful when the inside network is using a nonprivate address
space (unregistered usage of global address space) and you want it to connect to the
public network. Inside local addresses need to be translated to legal global addresses.
Legal addresses from the outside that overlap those used on the inside network need
to be translated to unused and recognizable addresses in the inside network. Both
inside source and outside source translations must be configured on the NAT router.
Figure 8 on page 83 illustrates how the inside network is using the unregistered
global address space of 15.12.0.0/16. Outside hosts whose addresses overlap with
this subnetwork that want to access the inside network need their global addresses
translated.

Figure 8: Twice NAT Example

To configure this example:
1.
2.
3.
host1:blue(config)#ip route 192.32.6.0 255.255.255.192 null 0
Enter the correct virtual router context.
host1(config)#virtual-router blue
Mark the inside interface.
host1:blue(config)#interface fast-ethernet 6/1
host1:blue(config-interface)#ip nat inside
host1:blue(config-interface)#exit
Mark the outside Interface.
host1:blue(config)#interface atm 3/0.20
host1:blue(config-interface)#ip nat outside
Chapter 2: Configuring NAT
NAT Configuration Examples
83