NAT Configuration Examples

When the network topology prevents direct connections between terminals and the server components, the streams need to be relayed using Network Address Translation (NAT).

In this case, the system is partially divided into network locations – parts of the network for which direct streaming towards others is not possible. System recognizes the endpoints belonging to a location and routes the call streams accordingly: the calls within a location need not to be routed as the calls between two locations are routed via MRS.

There is no need to divide the whole system (all users/trunks) into locations, only the users/trunks for which the specific switching rules are required. There may be any number of locations and the location contents may be configured in different ways.

To configure NAT:

1. Make sure there is at least one MRS module available for NAT. If necessary, install it with Infrastructure Administrator (IA)

   Note:

   MRS used for the NAT location does not need the option Use for Server-Side Recording.

   We recommend that you reserve different MRS modules for NAT, prompt playing, and recording. If you use the same MRS for different purposes, it is possible that recording reserves the MRS so that calls to the NAT location cannot be delivered. Make sure you define Maximum Number of Simultaneous Recordings and Maximum Number of Simultaneous Prompts in IA so that MRS can manage all necessary streams.

2. To create a NAT location, start the System Configurator (SC) and choose Call Switching > Locations, and carry out the following steps..

   • Click Add New and enter the name and description.

   • Choose the option Network Address Translation (NAT). If you define the switching rule as well, choose also Routing.

   • Define the location contents in one or more of the ways of IP Ranges, Network Elements, or Users.

   • Allocate the MRS module for NAT in the MRS Allocations block.

     Item	Description
     MRS Module	Select the MRS module from the list. Note: If the Firewall IP, User IP and Use Bypass settings are taken into use as well, dedicate this MRS module only for NAT.
     Priority	If several MRS modules are used, add the priority as an integer number, for example 50, 60, 70. Priority defines in which order the MRS servers are used for this purpose. One MRS can handle up to 800 streams simultaneously, define the priorities of different MRS modules so that the performance is optimal, and other MRS functions are not compromised.
     Firewall IP	Define the IP address that is shown for elements in the NAT location. This option is useful when a firewall/router exists between the location and MRS module.
     User IP	Define the IP address that is shown for the system. This option is useful when the MRS server resides in the network border, and for example, has separate network interfaces towards the users.
     Maximum Number of Simultaneous NAT Streams	Define how much resources the system reserves from the MRS module. The value should be at least the same as the number of simultaneous NAT calls expected to be routed via this MRS. The default value is 100. Note: If there are more than one Call Dispatcher (CD) modules in the system, they all reserve the defined number of streams. For example, with two CDs and the Maximum Number of Simultaneous NAT Streams value 100, totally 200 simultaneous streams are reserved.
     Use Bypass	If the bypass is used, the MRS module waits for the first received packet from the NAT location and uses the received source address as a stream target, regardless of the one given in signaling. This option is useful when there is a firewall/router between the location and MRS. The firewall handles also the port address translation for users.

   • If the NAT location is used for location-based routing, define the Switching Rules as well.

   • Save your entries.

3. To take NAT into use:

   • Select the Use NAT checkbox in Call Switching > Global Switching Settings > NAT.

   • Save your entries.