In this blog, we will explore the simulation of PSTN resources. To test calls over a T1 PRI, we will need to setup a back to back T1 which has been discussed in previous blog entries. Both T1 gateways must be configured and operational. Recall that one T1 gateway will need to provide clock (network side), while the other T1 gateway will be received to receive clock (user side which is the default). The T1 interfaces need to be connected with a T1 crossover cable, not an Ethernet crossover cable. T1 and Ethernet crossover cables both use RJ-45 heads, but they have different pinout configurations. Ensure that the H.323 or MGCP T1 gateway configuration in Cisco Unified Communications Manager (CUCM) is setup with Significant Digits set to all.
T1-CAS (Channel Associated Signaling) and T1 PRI (ISDN Primary Rate Interface) can be tested, but an MGCP T1-CAS circuit cannot be configured to provide clocking. The network side of the T1-CAS simulation will always have to be configured in the Cisco router IOS. If you’re fortunate enough to have the two port T1 VIC, configure one of each so both can be tested. If you only have the one port T1 VIC cards; you’ll be able to test each functionality, but not at the same time.
MGCP T1 configuration: To add an MGCP gateway in CUCM, choose the Device menu and select gateway (Device > gateway). Click the Add New Gateway hyperlink and select the router model you’re using from the drop down menu. Select MGCP as the Device Protocol and click the Next button. Configure a domain name. A fully qualified domain name (FQDN) can be configured, but the FQDN must match what is configured on the router. The following router configuration example will be used:
Router#configure terminal
Router(config)#hostname SANESTER
Router(config)#ip domain-name TMB.COM
Based on the above router configuration, the MGCP gateway will need to be configured as SANESTER.TMB.COM. The show ccm-manager router IOS command can be used to verify the FQDN. Select a Call Manager Group after the FQDN is configured in CUCM and click the Insert button. You will now need to configure the hardware modules that are in the router. If you’re using a 2811 ISR, you will select the NM-4VWIC-MBRD to select one of the four built in HWIC slots. Click the Update button. You will now need to select the VIC cards that are populated in the router. After selecting the appropriate hardware types from the drop down menus (Subunit 0 through Subunit 4 for the ISR), click Update. Click the Endpoint Identifiers hyperlinks next to your T1 card selection to enter the T1 configuration. The Device Protocol drop down menu now appears. Select T1-CAS or T1-PRI from the drop down menu. Ensure that the other side of the T1 connection matches the Device Protocol configuration. You must select the Device Pool. Every other configuration item is optional. If you have configured class of service (CoS) restrictions, you will need to configure a Calling Search Space for inbound calls. One side of the connection will need to be configured with a Protocol Side of Network. When done, click Insert and Reset the gateway. The Insert and Update buttons in Call Manager 4.x have been changed to the Save button and/or icon beginning with CUCM 5.0.
The following router configuration will be required for the MGCP gateway to pull its configuration from the CUCM TFTP server component:
Router(config)#ccm-manager config
Router(config)#ccm-manager config server 192.168.100.1
Replace the IP Address used in the configuration example above to the IP Address of your CUCM server running the TFTP service. A configuration will be dynamically loaded into the router based on the CUCM gateway configurations.
The call routing setup will be similar to the one discussed in the last blog, but we will put the T1 gateway into a new Route Group called PSTN_RG. Once the PSTN_RG is created, we can create a new Route List called PSTN_RL and add the PSTN_RG to the PSTN_RL. Remember to Reset the Route List when configured and any time any changes are made to the Route Group Details (digit manipulation) in the Route List. If you have a multi-flex trunk (MFT) VIC with two T1 interfaces, I recommend creating a route group for each of them.
All of the Route Patterns configured in the last blog will need to be re-configured to point to the PSTN_RL. We’ll talk about FXS and FXO gateways in the next blog…
Dennis Hartmann, CCIE No. 15651, is a consultant with www.highpoint.com and author of Implementing Cisco Unified Communications Manager, Part 1. Dennis is also a lead instructor at Global Knowledge. Dennis has various certifications, including the Cisco CCVP, CCSI, CCNP, CCIP, and the Microsoft MCSE. Dennis has various specializations including unified communications, data center, routing & switching, service provider (MPLS and optical). Dennis has worked for various Fortune 500 companies, including AT&T, Sprint, Merrill Lynch, KPMG, and Cabletron Systems. He lives with his wife and children in Hopewell Junction, New York.
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