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Configuring GSM VoIP gateways with Cisco Call Manager
The present document is a step-by-step guide for configuring the GSM VoIP gateways 2N VoiceBlue Lite (VBL), 2N VoiceBlue Enterprise (VBE) and Cisco Call Manager (CCM) software IP PBX. It includes essential steps for interconnecting the two products rather than a detailed configuration analysis of all units.
What is 2N VoiceBlue?
The 2N VoiceBlue GSM VoIP gateway is an ideal complementary product to any SIP-based IP PBX. It's suitable for small and medium companies with IP infrastructure and for companies with international affiliates. With VoiceBlue you gain significant savings on outgoing and incoming calls from IP to GSM networks and backwards. Thanks to the efficient and powerful Least Cost Router (LCR), the VoiceBlue VoIP GSM gateway always chooses the cheapest possible way to route the call (according to GSM prefixes, free minutes on SIM cards etc.).Using the VoiceBlue GSM VoIP gateway you achieve complete independence when connecting to GSM networks and maintain 100% control of your GSM call costs. With the help of voice prompts and efficient Dynamic Clip Routing, the VoiceBlue fixed cellular terminal routes incoming GSM calls to the right IP phones.
What is 2N VoiceBlue Enterprise?
2N VoiceBlue Enterprise is a VoIP to GSM Gateway supporting SIP and H.323 at the same time. It is a complementary product to any SIP or H323 based IP PBX and can also be used as a substitute to any SIP based IP PBX because the SIP proxy server can be included.The VoiceBlue Enterprise fixed cellular terminal can be used not only as a gateway to GSM but also a protocol translator between the SIP and H.323 environments (the scheme below). As VoiceBlue Enterprise VoIP GSM gateway uses the Siemens MC75 module, it is capable of data transfer (GPRS and EDGE technologies are implemented) and therefore can serve as a gateway from your LAN to the Internet. A firewall is embedded to provide maximum security. There is an option of SMS sending and receiving through a web or SMTP/POP3 interface. If an external USB hard disc is added, VoiceBlue GSM router can serve as an SMS server for SMEs as well.
In this article we are going to deal with configuring VoIP GSM gateways and Cisco Call Manager system, connected in the way this scheme can resemble the practical application in the best possible way.
Letâ€™s imagine a company using CCM as the main exchange in its headquarters in the Czech Republic and having one branch office in UK. Together with CCM, there is 2N VoiceBlue GSM VoIP gateway installed in the company headquarters, which will be used to complete calls to local GSM network.
The branch office in UK is so small it does not pay off to equip it with the classical exchange and most of its employees are out of their offices most of the time. This implies that most of the communication between the headquarters and the branch office employees will be performed over mobile phones in the UK GSM network. For that reason the branch office exchange is replaced with the VoiceBlue Enterprise VoIP system, which will ensure PBX functions for employees and at the same time the connection to GSM network, together with SIP telephones located in the UK branch office. Thanks to the Internet connection of the headquarters and the branch office the calls between companies can be routed free of charge and calls to distant GSM networks can be charged locally. (To make it simple letâ€™s suppose there is an IP VPN created between the headquarters and the branch office so the whole operation will function in a transparent way.)
Now we have the scenario, but the question is what part individual elements in our model will play. First an internal numbering plan has to be created. To make it simple letâ€™s say, we will use four-digit numbering and all telephone numbers in the headquarters will start with 1XXX and all telephone numbers in the branch office will then be numbers starting with 2XXX. Furthermore letâ€™s say that all calls to numbers with prefixes 004206,004207,004208,6,7,8 will be routed to VBE IP address in the company headquarters, all calls starting with 00420 will be routed to CCM and calls with 0044 will be routed to VoiceBlue Enterprise. This way it is ensured that if somebody in the branch office calls the Czech number, the VoiceBlue Enterprise GSM VoIP gateway will send the call to CCM and vice versa.
In accordance with the previous it is possible to create a simple routing table for each device.
Tab. 1: Routing table in CCM
Tab. 2: Routing table in VoiceBlue Enterprise
We will start with what seems to be the most difficult, that is with CCM. We will not deal with the telephone installation and CCM configuration for communicating with them here â€¦ it is for an independent document. We are going to focus only on SIP Trunk configuration and routing rules creation.
SIP Trunk creation
SIP Trunk is a kind of virtual interface, which points at the IP address of a distant device. This interface only knows where its distant end is and what protocol it can use to communicate with it.
From the Main Menu select Device > Trunk
click on Add new trunk and select protocols
After clicking on Next, Trunk parameters are displayed.
Change parameters according to pictures and click on INSERT.
This way an interface for VoiceBlue GSM VoIP gateway in headquarters has been created.
In the same way create a trunk for VoiceBlue Enterprise VoIP GSM gateway, so finally the trunk list looks the same as in the following picture. To display data click on Find.
Creation of a routing table
From the Menu select Route Plan > Route Pattern/Hunt Pilot
Click on Add new route
Create the first route pattern according to our routing table for prefix 2 and a total number of digits 4. To make decisions CCM uses the algorithm similar to regular expressions. In our case a single expression, which is X and indicates any number, will do. So the expression in our case will look as follows: 2XXX.
Set values according to the picture and click on Insert.
Now create the rest of route patterns according to our routing table in order the route pattern printout can look as follows:
Configuring 2N VoiceBlue Enterprise GSM VoIP gateway
Now the headquarters has been configured. CCM knows which way to send calls to the Czech GSM networks and which way to the English ones. At the same time it also knows when somebody calls an internal line starting with 2, this will also be routed to England.
So we need to perform the configuration of the whole branch office in England, i.e. VoiceBlue Enterprise GSM VoIP gateway.
Configuring internal SIP telephones
Letâ€™s start with creation of environment for the branch office internal telephones. Letâ€™s suppose there are 4 SIP telephones in the branch office and numbers 2001, 2002, 2003 and 2004 will be assigned to them. Letâ€™s have a look how to do it right now.
From the Menu select User Management and click on Users
After adding the user, continue on Add user and proceed according to the following picture. Here Username represents the telephone number of the given telephone and Password is the password which SIP telephone will use to connect to the VoiceBlue Enterprise GSM VoIP gateway.
Continue in the same way also for the rest of phones so that finally the Users Table looks as follows:
Now you can register SIP telephones to this IP GSM gateway easily by setting VBE IP address in the SIP proxy field and by signing it in by the means of accounts we have just created. After finishing this action it is possible for telephones in the branch office to make phone calls among each other.
The internal SIP proxy has been configured in order to register SIP telephones and enable to make phone calls among each other.
Finally, letâ€™s move to the implementation of our routing table. Before creation of routing rules it is important to realize the way the routing functions inside the VBE. Basically, VBE has two routing tables, first of them being marked as SIP proxy Routing table and the second as LCR. The sequence of decision rules is indicated in the following picture.
So when the telephone registered to the internal SIP proxy wants to dial a random number, it sends the INVITE packet to VBE or to its internal SIP proxy server. It is processed in SIP proxy rules and then it is either transmitted directly to other SIP gateway or it is transmitted to the internal LCR in case we need to route the call either to GSM or to H.323 networks.
So first create routing rules in SIP proxy table. To configure a SIP proxy table click on Services > SIP proxy.
Here create two routes, one to the internal LCR table to route calls to GSM and one to CCM in the company headquarters.
So the call with prefix 0044 will be routed to LCR through the internal SIP line.
The call to the headquarters will be transmitted to Call Manager IP address.
And so will all calls from the range of local numbers in the headquarters
After all settings the routing table in SIP proxy should assumedly look as follows:
Now LCR table has to be adjusted. Before defining a routing table it is necessary to create the route for this direction. In VBE the routes to GSM network are represented by GSM group. To make it simple, letâ€™s suppose we have SIM cards with the same tariff from one operator and therefore only one GSM group is to be created. See VBE manual for more complex configurations.
To create GSM group proceed as follows:
From the Menu select Configuration > LCR > GSM group
Name the group at your discretion and mark all GSM modules you want to use.
After adding the group there should be the following printout in the GSM groups list.
Now there are no obstacles to create a LCR table. In LCR section click on ADD button and proceed according to pictures:
The prefix box contains the regular expression, which is suitable for any number starting with 0044.
In the next step a single outgoing group, which has been defined, will be selected automatically and therefore it is enough to enter by clicking on Add button. Your LCR table should look as follows:
This way the configuration in the branch office is completed and we should be able to get connected to headquartersâ€™ local numbers and to UK GSM networks both from the UK branch office and from the headquarters.
Configuring the 2N VoiceBlue Lite GSM VoIP gateway
In this section you can find the most basic steps to configure VoiceBlue Lite GSM VoIP gateway. For more information see the previous articles or the manual.
In order VB can accept calls routed to it from CCM we have to insert CCM IP address to the SIP proxy field in ethernet parameters section.
At the same time forbid the registration by inserting 0 to the fields Registration expires and Reattempt registration.
Create a network list for numbers starting with prefix 00420.
And finally create add record to LCR table.
At that moment everything should function according to our scenario.
However, in case you face any trouble, go through the whole configuration making sure you did not forget about anything and if you do not eliminate the trouble you can always contact firstname.lastname@example.org which is free of charge for all 2N Telekomunikace customers.
Jan Mastalir, DiS
2N Telekomunikace a. s.
Created by: batikova, Last modification: Thu 04 of Aug, 2005 (08:52 UTC)
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