Static Net-To-Net Nat - 3Com 3C13636 Configuration Manual

3Com Router 3000 Ethernet Family
Configuration Guide
192.168.1.3 192.168.1.3 192.168.1.3 192.168.1.3
PC PC PC PC
Server Server Server Server
192.168.1.2 192.168.1.2 192.168.1.2 192.168.1.2
Figure 11-2 NAPT allowing multiple internal hosts to share a public address
As shown in the above figure, four data packets from internal addresses arrive at the
NAT server. Among them, packet1 and packet2 come from the same internal address
with different source port number, pakcet3 and packet4 come from different internal
addresses with an identical source port number. After the NAT mapping, all the 4
packets are translated into an identical public address with different source port
numbers, so they are still different from each other. As for the response packets, the
NAT server can also differentiate these packets based on their destination addresses
and port numbers and forward the response packets to the corresponding internal
hosts.

11.2.3 Static Net-to-Net NAT

Static net-to-net NAT maps an internal network address range to a public network
address range. This approach to NAT only involves the net ID portion of the IP address.
The host ID portion remains unchanged after address translation.
Static net-to-net NAT allows an internal host to access an external network through and
to be accessed at its associated public address.
Static net-to-net NAT creates direct mapping between internal host addresses and
public network addresses, and implements the function similar to NAT server.
However, static net-to-net NAT requires a large IP address space since it holds a
one-to-one mapping between internal host addresses and public network addresses.
To save IP address resources, you can use it with conventional static or dynamic NAT
but should note to avoid address conflicts.
Datagram1 Datagram1
Datagram1 Datagram1 Datagram1 Datagram1
Source IP: 192.168.1.3 Source IP: 192.168.1.3
Source IP: Source IP: 202.169.10.1 Source IP: 202.169.10.1 Source IP:
Source port: 1537 Source port: 1537 Source port: 1537 Source port: 1537 Source port: Source port: 3001 Source port: Source port: 3001
Datagram2 Datagram2 Datagram2 Datagram2 Datagram2 Datagram2
Source IP: Source IP:
192.168.1.3 192.168.1.3 Source IP: 202.169.10.1 Source IP: Source IP: 202.169.10.1 Source IP:
Source port: 2468 Source port: 2468 Source port: 2468 Source port: 2468 Source port: Source port:3002 Source port: Source port:3002
192.168.1.1 202.169.10.1 192.168.1.1 202.169.10.1 192.168.1.1 202.169.10.1 192.168.1.1 202.169.10.1
Datagram3 Datagram3 Datagram3 Datagram3 Datagram3 Datagram3
Source IP:192.168.1.1 Source IP:192.168.1.1 Source IP: 202.169.10.1 Source IP: Source IP: 202.169.10.1 Source IP:
Source port: Source port: 1111 1111 Source port: Source port: 3003 Source port: Source port: 3003
Datagram4 Datagram4 Datagram4 Datagram4 Datagram4 Datagram4
Source IP:192.168.1.2 Source IP:192.168.1.2 Source IP: 202.169.10.1 Source IP: Source IP: 202.169.10.1 Source IP:
Source port: 1111 Source port: 1111
Source port: Source port:3004 Source port: Source port:3004
3Com Corporation
11-4
Chapter 11 NAT Configuration
202.120.10.2 202.120.10.2 202.120.10.2 202.120.10.2
Server Server Server Server
Internet Internet Internet Internet
202.120.10.3 202.120.10.3 202.120.10.3 202.120.10.3
PC PC PC PC