Cisco 642-437 - Questions & Answers

Explanation:
1) To configure the DHCP address pool name and enter DHCP pool configuration mode, use the following command in global configuration mode:

Router(config)# ip dhcp pool name - Creates a name for the DHCP Server address pool and places you in
DHCP pool configuration mode

2) To configure a subnet and mask for the newly created DHCP address pool, which contains the range of available IP addresses that the DHCP Server may assign to clients, use the following command in DHCP pool configuration mode:

Router(dhcp-config)# network network-number [mask | /prefix-length] - Specifies the subnet network number and mask of the DHCP address pool. The prefix length specifies the number of bits that comprise the address prefix. The prefix is an alternative way of specifying the network mask of the client. The prefix length must be preceded by a forward slash (/).
3) After a DHCP client has booted, the client begins sending packets to its default router. The IP address of the default router should be on the same subnet as the client. To specify a default router for a DHCP client, use the following command in DHCP pool configuration mode:

Router(dhcp-config)# default-router address [address2 ... address8] - Specifies the IP address of the default router for a DHCP client. One IP address is required; however, you can specify up to eight
addresses in one command line.

http://www.cisco.com/en/US/docs/ios/12_2/ip/configuration/guide/1cfdhcp.html#wp1000999

Explanation: Since the phone is getting the correct TFTP address, the next thing that needs to be verified is the TFTP Server path and IP Reachablity for the IP Phone to the TFTP Server. Once the TFTP settings has been verified, check if the files mentioned in the termxx.defaults.loads file is available in the TFTP Server for the phone to download.
http://www.cisco.com/en/US/docs/voice_ip_comm/cuipph/7960g_7940g/7_0/sip/english/administration/guide/7960trbS.html

Explanation: To identify the IP address and port through which IP phones communicate with a CiscoUnifiedCME router, use the ip source-address command in telephony-service or group configuration mode. This command enables a router to receive messages from CiscoUnifiedIPphones through the specified IP address and port. The CiscoUnifiedCME router cannot communicate with CiscoUnifiedCME phones if the IP address of the port to which they are attached is not configured.

Normally when you configure basic telephony-service parameters, then phone can register with CME although no DN will be assigned to them. You can disable this by using the no auto-reg-ephone command. After this command the phone which will try to register will receive message "Registration Rejected: No configuration entry.....".. When automatic registration is blocked, CiscoUnifiedCME records the MAC addresses of phones that attempt to register but cannot because they are blocked.
http://www.cisco.com/en/US/docs/voice_ip_comm/cucme/command/reference/cme_a1ht.html#
wp1031242

Explanation: MGCP is a plain-text protocol used by call-control devices to manage IP Telephony gateways.
MGCP is a master/slave protocol that allows a call control device to take control of a specific port on a gateway. With this protocol, the Cisco CallManager knows and controls the state of each individual port on the gateway. It allows complete control of the dial plan from Cisco CallManager, and gives CallManager per-port control of connections to the PSTN, legacy PBX, voice mail systems, POTS phones and so forth.
This is implemented with the use of a series of plain-text commands sent over User Datagram Protocol (UDP) port 2427 between the Cisco CallManager and the gateway.

Another concept relevant to the MGCP implementation with Cisco CallManager is PRI Backhaul. This occurs when Cisco CallManager takes control of the Q.931 signaling data used on an ISDN PRI. The one thing that distinguishes a PRI from other interfaces is the fact that the data that is received from the PSTN on the D-channel and needs to be carried in its raw form back to the Cisco CallManager to be processed.
The gateway does not process or change this signaling data, it simply passes it onto the Cisco CallManager through TCP port 2428. The gateway is still responsible for the termination of the Layer 2 data. That means that all the Q.921 data-link layer connection protocols are terminated on the gateway, but everything above that (Q.931 network layer data and beyond) is passed onto the Cisco CallManager.
This also means that the gateway does not bring up the D-channel unless it can communicate with Cisco CallManager to backhaul the Q.931 messages contained in the D-channel.

http://www.cisco.com/en/US/tech/tk1077/technologies_tech_note09186a00801da84e.shtml