Cisco Systems 78-11741-02 Wireless Office Headset User Manual


 
Configuring IP Addressing
Configuring Network Address Translation
IPC-44
Cisco IOS IP Configuration Guide
addresses from a rotary pool. Allocation is done on a round-robin basis, and only when a new connection
is opened from the outside to the inside. Non-TCP traffic is passed untranslated (unless other translations
are in effect). Figure 7 illustrates this feature.
Figure 7 NAT TCP Load Distribution
The router performs the following process when translating rotary addresses:
1. The user on host B (9.6.7.3) opens a connection to the virtual host at 1.1.1.127.
2. The router receives the connection request and creates a new translation, allocating the next real host
(1.1.1.1) for the inside local IP address.
3. The router replaces the destination address with the selected real host address and forwards the
packet.
4. Host 1.1.1.1 receives the packet and responds.
5. The router receives the packet, performs a NAT table lookup using the inside local address and port
number, and the outside address and port number as the key. The router then translates the source
address to the address of the virtual host and forwards the packet.
The next connection request will cause the router to allocate 1.1.1.2 for the inside local address.
To configure destination address rotary translation, use the following commands beginning in global
configuration mode. These commands allow you to map one virtual host to many real hosts. Each new
TCP session opened with the virtual host will be translated into a session with a different real host.
1.1.1.1:23
1.1.1.2:23
1.1.1.3:23
1.1.1.127:23
1.1.1.127:23
1.1.1.127:23
Inside Local IP
address:port
TCP
TCP
TCP
Protocol
Inside Global IP
address:port
9.6.7.5:3058
6.5.4.7:4371
9.6.7.3:3062
Outside Global
IP address:port
9.6.7.3
NAT table
1
B
C
DA
1.1.1.127
6.5.4.7
2
S4804
Intranet
5
SA
1.1.1.127
4
SA
1.1.1.1
Inside
1.1.1.1
Real
hosts
Virtual
host
1.1.1.2
1.1.1.3
1.1.1.127
3
DA
1.1.1.1