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on the Internet and can only be used for private networks. For example, if you tell
someone on the Internet to connect to you using a 192.168.x.x address, it will not
work. Instead, you must provide your real/Public IP Address.
WWhhaatt iiss NNAATT aanndd hhooww ddooeess iitt aaffffeecctt VVooIIPP??
Network Address Translation (NAT) allows multiple devices to share the same exter-
nal IP address to access resources on the Internet. NAT is typically used to allow all
the devices in a subscriber’s local area network to access the Internet through a router
with a single public IP address assigned by the Internet Service Provider.
If a VoIP device is sitting behind a NAT, the private IP address assigned to it is not
usable for communications with the entities outside the private network. The VoIP
device must substitute the private IP address information with the proper external IP
address/port in the mapping chosen by the underlying NAT to communicate with a
particular public peer address/port. TalkSwitch can automatically check for the cur-
rent public IP address and substitute the private IP address with the public address so
that VoIP traffic is properly routed through the NAT.
WWhhaatt’’ss tthhee ddiiffffeerreennccee bbeettwweeeenn aa SSttaattiicc IIPP AAddddrreessss aanndd
aa DDyynnaammiicc IIPP AAddddrreessss?? WWhhaatt
eeffffeecctt ddooeess tthhiiss hhaavvee oonn VVooIIPP??
A Static IP Address is an address that is permanently assigned to a device. Typically, a
Static IP Address has to be assigned by the network administrator or Internet Service
Provider (ISP).
A Dynamic IP Address is an address that is temporarily assigned to devices by a DHCP
or PPP server that maintains and assigns a pool of IP addresses.
When deploying VoIP devices, it’s best to have a Static Public IP Address as this pre-
vents destinations from becoming unreachable for periods of time when the IP
address changes. But since this can be an expensive option, TalkSwitch 48-CVA sup-
ports the ability to handle Dynamic Public IP addresses for the Internet connection.
TalkSwitch can automatically check for the current public IP address and substitute
the private IP address with the public address so that VoIP traffic is properly routed
through the NAT.
WWhhaatt iiss aa SSIIPP PPrrooxxyy aanndd RReeggiissttrraarr??
SIP’s basic architecture is client/server in nature. The main entities in the SIP server
are the Proxy, Redirect Server and the Registrar.
TalkSwitch 48-CVA has the SIP Server fully integrated for easy deployment and main-
tenance of your VoIP network. If you are deploying a multi-site configuration which
can comprise of TalkSwitch 48-CVA units, certified 3rd party gateways and certified
3rd party SIP phones, then one TalkSwitch 48-CVA can act as the SIP Proxy and
Registrar. The other SIP end-points will register with this TalkSwitch 48-CVA and all
calls will be negotiated through this TalkSwitch 48-CVA.
iv TalkSwitch User Manual
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