Home Lab (Voice Interface Cards)

You will most probably want to test gateway functionality in your home lab. To test this functionality, you will need to purchase some TDM (Time Division Multiplexing) hardware interfaces. The cheapest interface types are FXS and FXO analog interfaces. You will most probably want to purchase a foreign exchange station (FXS) card to test gateway functionality from an analog phone. FXS and FXO cards have RJ-11 connections, but they operate very differently. The FXS card generates dial tone to a device that expects to receive dial tone, while the FXO accepts dial tone. In a home environment with two routers, FXO to FXS connections can be used to test FXO functionality without analog phone connections from your PSTN provider. A simpler test environment will have one router with the FXO connected to the analog circuit at home provided by the PSTN provider. The local exchange carriers (LECs) and Voice over IP home services all provide RJ-11 connections in which an FXO connection could be connected. If the RJ-11 connection from the LEC or VoIP provider is connected to a wall jack in the house, the gateway’s FXO port can be connected to any phone jack in the home to terminate the call. I recommend the two port VIC2-FXO card for a home gateway, but the four-port VIC2-FXO can also be used in the ISR routers. The FXS card will be required to terminate any analog phones or fax machines at home. You will probably want to test the functionality of both phones and fax machines since both off low cost devices. The two port VIC2-2FXS will probably meet your needs, but the four port VIC2-4FXS card is used in many production environments to meet the analog device needs. The FXO and FXS VIC cards are probably all you want for a home-based one router voice lab. All connections between FXS/FXO cards and devices use standard straight-through wired RJ-11 phone cables. Unfortunately, we will not be able to test T1 interfaces in a one router lab configuration. A two router lab will want to add two VWIC-1MFT-T1 cards (one for each router). The T1 interface cards have 8-pin RJ-45 or RJ-48 connections. Standard Category 5 cabling can be used to connect the T1 interfaces, but they will need to be pinned out differently than standard straight through Category 5 cabling. Category 5 cabling is not a requirement. Any Unshielded Twisted Pair (UTP) category above category 5 will suffice for T1 connections. T1 voice interfaces use pins 1, 2, 4, and 5 for their transmission. Pins 1 and 2 are the receive (RX) pins, while pins 4 and 5 are the transmit (TX) pins. The T1 crossover cable should connect pins 1 and 2 to pins 4 and 5. http://www.ldfacts.com/faq_files/How-to-Make-a-T1-Crossover-cable.htm When configuring the T1 interfaces, the timing configuration of one side of the connection will need to be modified. One T1 interface will need to be configured to provide clock in the T1 controller configuration (clock source internal), while the other will use the default line timing (clock source line). The H.323 T1 gateway providing timing will also need the isdn protocol-emulate network command in interface Serial 0/0/0:23 configuration mode (assuming the T1 card is in slot 0). The MGCP gateway providing the timing will need to have the MGCP T1 endpoint configured with a Protocol Side of Network in the CUCM configuration pages. All T1 controllers default to line timing to get their timing from the service provider. E1 interfaces could be used in addition to or in the place of T1 interfaces. The Voice CCIE lab equipment list includes both T1 and E1 interfaces. If a Voice CCIE is your final goal, plan on buying two T1 VICs and two E1 VICs. The next blog entry will discuss WAN hardware interface types and how we can use IP Communicator to simulate a PSTN for testing dial plan configurations.