Determining Whether The Router Uses Symmetric Or Asymmetric Nat - Cisco SPA942 - - IP Phone Administration Manual

Configuring SIP, SPCP, and NAT
Network Address Translation (NAT) and Cisco IP Phones
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STEP 8
Cisco SPA and Wireless IP Phone Administration Guide
Determining Whether the Router Uses Symmetric or
Asymmetric NAT
STUN does not work on routers with symmetric NAT. With symmetric NAT, IP
addresses are mapped from one internal IP address and port to one external,
routable destination IP address and port. If another packet is sent from the same
source IP address and port to a different destination, then a different IP address
and port number combination is used. This method is restrictive because an
external host can send a packet to a particular port on the internal host only if the
internal host first sent a packet from that port to the external host.
This procedure assumes that a syslog server is configured and is ready to receive
syslog messages.
Make sure you do not have firewall running on your PC that could block the syslog
port (by default this is 514).
Log on to the phone's web UI. For information about this, see the
Administration User Interface" section on page
Click Admin Login > Advanced. (For WIP310, click Admin Login.)
Click the System tab, then set
your syslog server. Note that this address and port number has to be reachable
from the Cisco IP phone. This port number appears on the output file name. The
default port number is 514.
Set Debug Level to 3. Do not change the value of the
To capture SIP signaling messages, click the Ext tab.
SIP Debug Option
Set
port number was specified).
To collect information about what type of NAT your router uses click the SIP tab
and scroll to NAT Support Parameters.
Debug Server
to Full. The default output is named syslog.514.log (if not
"Using the Web
25.
to the IP address and port number of
Syslog Server
5
parameter.
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