CyberCertPrepNetwork FundamentalsIP Addressing & SubnettingEASYFree question
Scenario
A network technician is configuring a point-to-point WAN link between two routers. The IP addressing team allocated 192.168.100.0/30 for this link. The technician assigns 192.168.100.1/30 to Router A and 192.168.100.2/30 to Router B.
What are the network address and broadcast address for this /30 subnet, and how many usable host addresses does it provide?
- A.Network: 192.168.100.0, Broadcast: 192.168.100.7, Usable: 6 hosts
- B.Network: 192.168.100.0, Broadcast: 192.168.100.3, Usable: 2 hosts
- C.Network: 192.168.100.1, Broadcast: 192.168.100.2, Usable: 2 hosts
- D.Network: 192.168.100.0, Broadcast: 192.168.100.255, Usable: 254 hosts
Why B is correct
/30 mask = 255.255.255.252. Block size = 4. Starting at 0: Network=192.168.100.0, hosts .1 and .2, Broadcast=192.168.100.3. Usable = 2^2 − 2 = 2 hosts. /30 is the traditional point-to-point link subnet. RFC 3021 defines /31 as an alternative (2 addresses, no network/broadcast needed for point-to-point), giving the same 2 usable host addresses without wasting the network and broadcast addresses.
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