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(00)access-group
......
(09)nat
......
Please Input the code of command to be excute(0-18): 9
Input 9, select nat option, prompt is as below:
(00)inside
(01)outside
Please Input the code of command to be excute(0-1): 1
Input 1,select outside option, it will sign the interface to be connected to outside network.
Note:
The access list must permit only those addresses that are to be translated. (Remember that there is an implicit "deny all" at
the end of each access list.) An access list that is too permissive can lead to unpredictable results.
See the "Translating Overlapping Address Example" section at the end of this chapter for an example
of translating an overlapping address.
6.3.12 Providing TCP Load Distribution
Another use of NAT is unrelated to Internet addresses. Your organization may have multiple hosts that
must communicate with a heavily used host. Using NAT, you can establish a virtual host on the inside
network that coordinates load sharing among real hosts. DAs that match an access list are replaced
with 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). Figuer 6-4 illustrates this feature.
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.
Specify access control for packets
NAT interface commands
Inside interface for address translation
Outside interface for address translation
NAT TCP Load Distribution
Figuer 6-4
Model Name
- 171 -
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