User's Manual

Configuring Network Address Translation
308625-14.00 Rev 00
2-5
When the router’s NAT interface receives a packet, the NAT router extracts the
source address, first checking whether the packet’s source address falls within a
configured local address range. If it does, NAT compares the source address
against existing address translation entries in an internal table. In Figure 2-2
, the
NAT router detects a packet on a NAT interface that contains the address
10.0.0.15.
Figure 2-2. NAT Detects the Source Address
If the inside host’s source address does not appear in the translation table and is
within a configured local address range, the NAT router does the following:
1.
Creates a new entry for the host
2.
Dynamically assigns the next available registered IP address from a global
address pool
3.
Changes the source address of the packet to the registered address
NAT router
Local address
range list
Global address
range list
15.0.0.0 to 15.255.255.255
50.1.1.0 to 50.1.1.255
192.55.10.0 to 192.55.10.255
192.20.10.0 to 192.20.10.255
Current local/global
mapping entry list:
10.0.0.1 192.55.10.1
10.0.0.2 192.55.10.2
10.0.0.15 192.100.20.2
IP packet
Source address Destination address
IP0052A
10.0.0.0 to 10.255.255.255