What is the network address of 192.0.2.173/28?
A 192.0.2.160
B 192.0.2.144
C 192.0.2.168
D 192.0.2.172
Answer: A. 192.0.2.160. A /28 advances in blocks of 16; .173 lies in the .160–.175 block.
For 192.0.2.173/28, what is the directed broadcast address?
A 192.0.2.174
B 192.0.2.191
C 192.0.2.175
D 192.0.2.159
Answer: C. 192.0.2.175. The /28 block containing .173 runs from .160 through .175; the final address is broadcast.
How many total IPv4 addresses are in a /22 block?
A 2,048 addresses
B 1,024 addresses
C 256 addresses
D 512 addresses
Answer: B. 1,024 addresses. A /22 leaves 10 host bits, giving 2^10 or 1,024 addresses.
For subnet 172.16.20.0/22, what is the broadcast address?
A 172.16.20.255
B 172.16.22.255
C 172.16.21.255
D 172.16.23.255
Answer: D. 172.16.23.255. A /22 advances by four in the third octet; the block from 20 through 23 ends at .23.255.
How many conventional usable host addresses does a /29 provide?
A 8 hosts
B 4 hosts
C 6 hosts
D 14 hosts
Answer: C. 6 hosts. A /29 has eight addresses; excluding network and broadcast leaves six usable hosts.
What is the address-block size for a /27 subnet?
A 32 addresses
B 128 addresses
C 64 addresses
D 16 addresses
Answer: A. 32 addresses. A /27 leaves five host bits, so each block contains 32 addresses.
How large is the fixed IPv6 base header?
A 20 bytes
B 32 bytes
C 60 bytes
D 40 bytes
Answer: D. 40 bytes. The fixed IPv6 base header is 40 octets, before any extension headers.
Who may fragment an oversized IPv6 packet for delivery?
A The destination router
B The source node
C A DNS resolver
D Every transit router
Answer: B. The source node. IPv6 fragmentation is performed by the source, not by routers along the path.
Which protocol carries IPv6 Neighbor Discovery messages?
A ICMPv6
B ARP
C UDP
D TCP
Answer: A. ICMPv6. Neighbor Discovery is defined using ICMPv6 messages.
What is a Neighbor Solicitation commonly used to determine?
A Remote DNS server
B IPv4 broadcast address
C Neighbor link-layer address
D TCP window size
Answer: C. Neighbor link-layer address. Neighbor Solicitation helps discover a neighbor’s link-layer address on the same link.
What does the IPv4 header checksum cover?
A Ethernet frame
B Payload and header
C TCP data only
D IPv4 header only
Answer: D. IPv4 header only. The IPv4 checksum covers only the IPv4 header, not the payload.
IPv4 fragment offsets are measured in what units?
A 16-octet units
B 8-octet units
C 4-octet units
D 1-octet units
Answer: B. 8-octet units. The fragment offset field counts units of eight octets.
What does the IPv4 DF flag require?
A Always fragment
B Discard every packet
C Use IPv6 routing
D Do not fragment
Answer: D. Do not fragment. When DF is set, IP fragmentation is not permitted; the datagram may be discarded if too large.
Which checksum is absent from the IPv6 base header?
A UDP length
B Payload length
C Header checksum
D TCP checksum
Answer: C. Header checksum. IPv6 removed the base-header checksum to simplify forwarding.
Which prefix is reserved for IPv6 link-local unicast?
A FE80::/10
B FC00::/7
C FF00::/8
D 2000::/3
Answer: A. FE80::/10. IPv6 link-local unicast addresses use the FE80::/10 prefix.
Which prefix identifies IPv6 multicast addresses?
A FE80::/10
B FF00::/8
C FC00::/7
D 2000::/3
Answer: B. FF00::/8. IPv6 multicast addresses begin with the FF00::/8 prefix.
What security service does DNSSEC add to DNS data?
A Client anonymity
B Query confidentiality
C Traffic compression
D Origin authentication and integrity
Answer: D. Origin authentication and integrity. DNSSEC provides data-origin authentication and integrity, not confidentiality.
How does BGP detect many AS-path loops?
A Checks its own AS number
B Tests TCP ports
C Compares DNS TTLs
D Counts Ethernet frames
Answer: A. Checks its own AS number. A BGP speaker checks whether its own AS number appears in the AS_PATH.
Routes include 10/8, 10.1/16, and 10.1.2/24. Which matches 10.1.2.50 best?
A 10.0.0.0/8
B 10.1.0.0/16
C 10.1.2.0/24
D 0.0.0.0/0
Answer: C. 10.1.2.0/24. The /24 is the longest, most specific prefix matching the destination.
TCP sequence numbers operate in which number space?
A Modulo 2^16
B Modulo 2^32
C Modulo 2^64
D Modulo 2^8
Answer: B. Modulo 2^32. TCP sequence numbers are 32-bit values and wrap modulo 2^32.
With MTU 1,500 and 20-byte IPv4/TCP headers, what is MSS without options?
A 1,500 bytes
B 1,440 bytes
C 1,480 bytes
D 1,460 bytes
Answer: D. 1,460 bytes. Subtract the 20-byte IPv4 and 20-byte TCP headers from the 1,500-byte IP MTU.
When an IPv4 router discards a packet after TTL reaches zero, which ICMP type is commonly sent?
A Time Exceeded
B Echo Reply
C Source Quench
D Redirect
Answer: A. Time Exceeded. ICMP Time Exceeded reports that the packet’s time-to-live expired in transit.
An ACK number of 5,001 usually indicates what in TCP?
A Next port selected
B Last byte received
C Next byte expected
D Window scale factor
Answer: C. Next byte expected. A cumulative TCP acknowledgment identifies the next sequence number expected.
What does a TCP FIN indicate?
A Confirm frame checksum
B No more sender data
C Request a DNS lookup
D Reset the whole route
Answer: B. No more sender data. FIN indicates that the sender has no more data to send on that direction of the connection.
What does a TCP RST normally signal?
A Normal half-close
B Successful DNS answer
C Connection reset
D IPv4 fragmentation
Answer: C. Connection reset. RST resets a TCP connection rather than performing an orderly FIN close.