Which series of commands secures the router from the hackers?

Hackers are sending calls through a gateway router that is running SIP. The engineer blocks all SIP messages to the router except from their SIP server, which has an IP address of 208.177.10.1. The customer also must connect via SIP to their Cisco Expressway server with an IP address of 10.1.10.110.

Which series of commands secures the router from the hackers?
A . voice service voip
voip security allow
ipv4 208.177.10.1 255.255.255.255
ipv4 10.1.10.110 255.255.255.255
B . voice service voip
ip address trusted list
ipv4 208.177.10.1 255.255.255.255
ipv4 10.1.10.110 255.255.255.255
C . voice service voip
allow-connections sip to sip
ipv4 208.177.10.1 255.255.255.255
ipv4 10.1.10.110 255.255.255.255
D . voice service voip
address-hiding
ipv4 208.177.10.1 255.255.255.255
ipv4 10.1.10.110 255.255.255.255

View Answer

Answer: B

Explanation:

Reference: http://www.cisco.com/c/en/us/support/docs/voice/call-routing-dial-plans/112083-tollfraud­ios.html