Netopia 3346N-ENT User Guide (en)

4-4  Firmware User Guide
Exterior addresses are allocated to internal hosts on a demand, or as-needed, basis and then made available 
when traffic from that host ceases. Once an internal host has been allocated an address, it will use that 
address for all traffic. Five minutes after all traffic ceases – no pings, all TCP connections closed, no DNS 
requests, etc. – the address is put at the head of an available list. If an interior host needs an exterior address 
an hour later, and the previously used address is still available, it will acquire the same address. If an interior 
host that has not previously been allocated an exterior address needs one, it will be allocated the last, hence 
the oldest, exterior address on the available list.
All NAT configurations are rule-based. This means that traffic passed through NAT from either the public or the 
private network is compared to the rules and mappings configured in the Netopia Router in a par ticular order. 
The first rule that applies to the traffic being initiated is used. 
For example, if a connection is initiated from the public network and is destined for a public IP address 
configured on the Netopia Router, the following comparisons are made in this order. 
The Netopia Router first checks its internal NAT cache to see if the data is par t of a previously initiated 
connection, if not…
The Netopia Router checks the configured ser ver lists to see if this traffic is intended to be for warded to an 
internal host based on the type of ser vice. 
The Netopia Router then checks to see if there is a static, dynamic, or PAT mapping for the public IP 
address that the connection is being initiated to. 
The Netopia Router answers the request itself if the data is destined for the Netopia’s WAN inter face IP 
address. Other wise the data is discarded.
Network Address Translation
Available for Dynamic NAT
Used for Normal NAT
WAN Network
LAN Network