Zhone 2208 Guia Do Utilizador

Página de 247
A p p l i c a t i o n s   N o t e s
C-3
Accessing the Internet from the LAN
When you want to access the Internet from the LAN, but do not want to 
access any local LAN devices from the Internet, enable NAT translation on 
the WAN port that is connected to the Internet Service Provider (ISP). If two 
ATM PVCs are defined and one of these is connected to a voice gateway, the 
PVC connected to the ISP should have NAT enabled.
Configuring NAT Port Range
When you access the internet from the LAN, the request uses the next unused 
port number in the configured NAT port range. For most applications, the 
default range of 30000 through 65535 will work, as these port numbers are 
not commonly used. If any port numbers in this range are used (i.e., 
multiplayer Internet games), the range must be adjusted. The number of 
concurrent requests through NAT is limited by the size of the range. For 
current port number assignments, please refer to http://www.iana.org/
assignments/port-numbers.
Configuring NAT TCP Timeout
When a TCP connection is made through NAT, a context block is allocated 
from the IAD’s memory. This context block is freed when either the TERM 
bit is seen in the TCP header, or when the timeout period has been exceeded 
with no data. In most applications, the default value of 5 min (300 s) will be 
sufficient. If the application features a large number of aborted TCP 
connections, this value may need to be lowered. If the application features 
connections with longer idle times, this value may need to be increased.
Configuring NAT UDP Timeout
When a non-TCP connection is made through NAT, a context block is 
allocated from the IAD’s memory. This context block is freed when the 
timeout period has been exceeded with no data. In most applications, the 
default value of 2 min (120 s) will be sufficient. If the application features a 
large number of very short UDP, AH, or ESP connections, this value may 
need to be lowered. If the application features connections with longer idle 
times, this value may need to be increased.
Accessing LAN Devices from the Internet
If you want to access a LAN device from the Internet (i.e., Web server, FTP 
server, etc.), the device must be configured in NAT to allow access from the 
Internet. There are two ways to do this: through a NAT Local Server entry or 
through a NAT Alias entry.
NAT Local Server Configuration
A NAT Local Server entry is used when the local device shares its IP address 
with the WAN port of the IAD. Only the configured protocol and port will be