200-301: Cisco Certified Network AssociateDemo

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QuestionQ135

IP Connectivity

An engineer must configure a /30 subnet between two routers. Which usable IP address and subnet mask combination satisfies this requirement?

  • A interface e0/0 description to XX-AXXX:XXXXX ip address 10.2.1.3 255.255.255.252
  • B interface e0/0 description to XX-AXXX:XXXXX ip address 192.168.1.1 255.255.255.248
  • C interface e0/0 description to XX-AXXX:XXXXX ip address 172.16.1.4 255.255.255.248
  • D interface e0/0 description to XX-AXXX:XXXXX ip address 209.165.201.2 225.255.255.252
Explanation

A /30 network uses the mask 255.255.255.252 and provides exactly two usable host addresses, the first and second addresses in the block, with the last address reserved for broadcast. For the 209.165.201.0/30 subnet, .1 and .2 are usable, so .2 is a valid point-to-point interface address. By comparison, 10.2.1.3/30 is the broadcast address of the 10.2.1.0/30 subnet (not usable), and 255.255.255.248 defines a /29, not the required /30.

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