Specifications

Features
IP Telephony
154 Strata CIX General Description 08/14
Network Address Translation (NAT)
The Strata CIX supports the use of IP telephones that are behind NAT firewalls. NAT allows
multiple devices, such as personal computers and IP telephones to share a single public IP address.
This is very common in home and small office broadband networks. A Strata CIX in the main
office is able to support IP telephones at remote offices that are behind broadband routers and not
connected by VPN – something not supported by some VoIP vendors. Of course using a VPN is
more secure, but there may be instances where it is not practical. If you would like to support a
mix of devices on the private network, and devices on the public network, see the guidelines
below.
NAT Firewall Guidelines
The use of a firewall between the Strata CIX, LAN or Media Application Server and the Public
Internet is highly recommended. However, the use of some firewalls or routers with NAT requires
proper configuration to avoid problems with IPTs registered to an MIPU / LIPU card.
NAT General Guidelines
The following are general guide lines for successful IPT configuration.
• All MIPU / LIPU / GIPU and GIPH cards must have a Public IP Address if there are any public
network IPTs. This allows the MIPU / LIPU and GIPU / GIPH to resolve the NAT translated IP
addresses of both IPTs involved in the call.
This also allows you to configure an IP phone or soft IPT to work on the LAN and have the
same configuration work when you take the phone or laptop to another network.
• There must not be more than one NAT router between an IPT and the internet.
• The MIPU / LIPU and GIPU / GIPH must have a Gateway Address assigned.
• The MIPU / LIPU and GIPU / GIPH should be connected to the public network, through a
firewall. The firewall should use a one-to-one NAT to give the MIPU / LIPU and GIPU / GIPH
the same IP address on the public side and the safe side of the firewall.
• The MIPU / LIPU and GIPU / GIPH can not be located ‘behind’ a NAT (given a private IP
address). However, it can, and should be behind a firewall.
NAT Router Guidelines
There are three types of NAT routers available at this time.
• Full Cone — These are compatible with Strata CIX and Strata Net IP configurations.
• Partial/Restricted Cone — These are compatible with Strata CIX and Strata Net IP
configurations.
• Symmetric — At this time these routers may cause unreliable service or cause unwanted
symptoms. These routers are not compatible with Strata CIX and Strata Net IP configurations.