You issue the no ip source-address 172.16.0.1 command in telephony service configuration mode on a CME
router.
Which of the following is true? (Select the best answer.)

A.
The CME router will no longer receive credential services messages.

B.
The CME router will receive IP phone messages through an alternate port.

C.
The CME router will no longer receive messages from IP phones.

D.
The CME router will receive messages from IP phones by using IPv6.

Explanation:
The Cisco Unified Communications Manager Express (CME) router will no longer receive messages from IP
phones if you issue the no ip sourceaddress 172.16.0.1 command in telephony service configuration mode. The
syntax of the ip sourceaddress command is ip sourceaddress {ipv4address | ipv6address}, where ipv4address
is the IP version 4 (IPv4) address on which you want the router to receive IP phone messages. Issuing the no
form of this command disables the CME router’s ability to receive messages from IP phones.
The CME router will not receive IP phone messages through an alternate port. To configure the CME router to
receive IP phones through an alternate port, you should issue the ip sourceaddress command with the port
keyword. However, the port keyword applies only to Skinny Client Control Protocol (SCCP) phones and
operates only on an IPv4 address. For example, issuing the ip sourceaddress 172.16.0.1 port 2400 command
in telephony service configuration mode configures the CME router to receive IP phone messages on
172.16.0.1 on Transmission Control Protocol (TCP) port 2400. If the portkeyword is not specified, the CME
router receives the IP phone messages on TCP port 2000.
The CME router will not receive messages from IP phones by using IPv6. In order to configure the CME router
to receive messages from IP phones by using IPv6, you should issue the ip sourceaddress command with an
IPv6 address instead of an IPv4 address. You can also configure the source address to operate in dualstack
mode by issuing the secondary keyword followed by an IPv4 address. For example, the ip sourceaddress
2001:DB8:A::1 secondary 172.16.0.1 command configures the CME router to receive IP phone messages at
either the IPv6 address of 2001:DB8:A::1 or the IPv4 address of 172.16.0.1.
You cannot configure whether the CME router will receive credential services messages from telephony service
configuration mode. Issuing the ip sourceaddressipaddresscommand in credentials configuration mode
configures the CME router to receive credential services messages from a particular IP address. Issuing the no
form of this command in credentials configuration mode disables that ability.

https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucme/command/reference/cme_cr/
cme_i1ht.html#wp3725679205