PLANET VIP-350PT - Manual (Page 90)

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Diagnose NAT
Detect the NAT IP and the NAT type this UA is currently behind (8 possibilities).
The IP Phone will communicate with the STUN server (running outside the NAT, assigned in
“6.Network” / “Firewall & NAT” / “STUN Server”) to determine the type of NAT it is behind and
the diagnosis may take a quite while (roughly 10 seconds or so in a worse case). If the phone fails
to contact a STUN server, it will report it as “No STUN server is available”; otherwise, it will show
the IP of the NAT / firewall.
• Public internet (Neither NAT nor Firewall is involved)
• Firewall blocks UDP (Definitely, you cannot communicate with parties outside of your
LAN!).
• Symmetric UDP Firewall (STUN may work!)
Firewall that allows UDP out and responses have to come back to the source of the
request (like a symmetric NAT, but no translation. We call this a symmetric UDP
Firewall).
• Full cone NAT (Enable STUN should suffice).
A full cone NAT is one where all requests from the same internal IP address and port
are mapped to the same external IP address and port. Furthermore, any external host
can send a packet to the internal host, by sending a packet to the mapped external
address.
• Restricted cone NAT (STUN may work!)
A restricted cone NAT is one where all requests from the same internal IP address and
port are mapped to the same external IP address and port. Unlike a full cone NAT, an
external host (with IP address X) can send a packet to the internal host only if the
internal host had previously sent a packet to IP address X.
• Port restricted cone NAT (STUN may work!)
A port restricted cone NAT is like a restricted cone NAT, but the restriction includes port
numbers. Specifically, an external host can send a packet, with source IP address X
and source port P, to the internal host only if the internal host had previously sent a
packet to IP address X and port P.
• Symmetric NAT
A symmetric NAT is one where all requests from the same internal IP address and port,
to a specific destination IP address and port, are mapped to the same external IP
address and port. If the same host sends a packet with the same source address and
port, but to a different destination, a different mapping is used. Furthermore, only the
external host that receives a packet can send a UDP packet back to the internal host.
• Non full cone NAT
If failed to identify the NAT type, it will show “Non Full cone NAT” (such as the one
bundled in Win2000).
Í
Note
This may also be a false alarm if the specifed STUN server is either down or
unreachable.