Home Lab (PSTN Simulation)

To simulate a wide area network (WAN), two routers will be required. The WIC-1T card will give you one WAN interface with a DB-60 connector. Back to back serial cables with DB-60 connectors can be purchased on E-Bay. I recommend searching for the term “back to back serial” on E-Bay to find cables. Make sure the cables have two DB-60 connectors. The WIC-2T card offers two WAN interfaces, but uses the Cisco Smart Serial connectors. The smart serial connectors allow higher port densities to be used on the WAN interface card (WIC) slots. Verify that you are ordering the proper cables to connect your WICs. Smart Serial to DB-60 connected back to back cables are available for purchase online. Now that we have the hardware options out of the way, it’s time to build a lab environment in which we can simulate a Public Switched Telephone Network (PSTN). In a one router solution with limited voice interfaces, I recommend connecting to your PSTN provider and routing calls to the PSTN. This conversation will evolve into testing T1-CAS, PRI, FXO, and FXS connections in a two router test lab environment with two Cisco Unified Communications Manager (CUCM) clusters, but we will start with the endpoint configurations and then route calls over the IP WAN. To properly test this dial plan, we will need to configure a software phone (IP Communicator) as the third phone in the pod. This phone will accommodate up to eight phone numbers since IP Communicator is modeled after the 7970 phone which includes 8 buttons for lines, speed dials, Service URLs, and programmable line keys (PLK). The IP Communicator configuration should include a 3-digit, 7-digit, 10-digit, 11-digit, and International pattern of your choosing. An example of this would be 411, 7381450, 9147381450, 19147381450, and 011338088. One IP Communicator will be used in each cluster for a total of two IP Communicators. Each IP Communicator will need unique phone numbers which will be attempted from the partner pod. Now that each lab has some PSTN phone numbers that can be reached, we will be able to test calls in the future. Assuming that the WAN between the routers has been configured with IP addresses and a routing protocol is running, we will create non-gatekeeper controlled inter-cluster trunks between the two CUCM clusters to route calls over the IP WAN. Provision the above mentioned trunks from the Device > Trunk menu in Call Manager administration (ccmadmin). Name the trunk something creative to describe the destination CUCM cluster you are pointed at. Star Wars geeks may enjoy using Endor and Hoth to indicate two different CUCM clusters. Point the trunk to the IP Address of the remote CUCM server. Click Save and Reset the trunk. Create a Route Group from ccmadmin: Call Routing > Route/Hunt > Route Group and name the Route Group WAN_RG. The distribution algorithm does not matter at this time since there is only one device in the Route Group. Add the trunk to the WAN_RG. Click Save. Add a Route List from ccmadmin: Call Routing > Route/Hunt > Route List. Name the Route List WAN_RL and add the WAN_RG to the Route List. Click Save and Reset. You will now provision five route patterns to simulate a real world PSTN dial plan. Each Route Pattern will point to the WAN_RL. The Route Patterns to simulate a PSTN dial plan will be as follows: 911 9.911 9.[2-8]11 9.[2-9]xxxxxx 9.[2-9]xx[2-9]xxxxxx 9.1[2-9]xx[2-9]xxxxxx 9.011! 9.011!# After each of the router patterns has been added, the calls to the phone numbers that are configured on IP Communicator can be attempted from a phone on the other cluster. The IP Communicator phone should ring if everything has been properly configured. In the next blog, we will use this same call routing concept, but we will route calls the traditional telephony voice interfaces on the gateway routers.

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