Unit 4: Routing and IP Header - Practice Quiz

1 What is the main purpose of a routing algorithm?

2 Which device commonly uses routing algorithms to forward packets between networks?

3 What does a shortest path algorithm find in a network?

4 Which algorithm is commonly used to compute shortest paths in link state routing?

5 In a network graph, what does an edge usually represent?

6 What information does a router share with its neighbors in distance vector routing?

7 Which algorithm is the basis of distance vector routing?

8 Which problem is commonly associated with distance vector routing?

9 What does each router build in link state routing?

10 How is link state information normally distributed to routers?

11 Which routing protocol uses a link state approach?

12 How many bits are in an IPv4 address?

13 Which IPv4 header field limits how long a packet can remain in the network?

14 Which IPv4 header field helps detect errors in the header?

15 How many bits are in an IPv6 address?

16 Which IPv6 header field serves a purpose similar to the IPv4 Time to Live field?

17 What is the fixed size of the basic IPv6 header?

18 Which notation is normally used to write an IPv6 address?

19 What does :: represent when used in an IPv6 address?

20 What is the main function of Network Address Translation (NAT)?

21 A network's link delays vary significantly with traffic load. Which routing approach is most suitable for selecting routes based on current conditions?

22 A router has routes for 10.0.0.0/8 via A, 10.1.0.0/16 via B, 10.1.2.0/24 via C, and 0.0.0.0/0 via D. Where is a packet for 10.1.2.130 forwarded?

23 An undirected graph has edges A–B with cost 4, A–C with cost 1, C–B with cost 2, B–D with cost 1, and C–D with cost 5. What is the shortest route from A to D?

24 During Dijkstra's algorithm, node U has tentative distance 7 and is selected next. Its edge to V has cost 3, while V currently has tentative distance 12. What value should be assigned to V?

25 Router X reaches neighbor A with cost 2 and neighbor B with cost 5. A advertises distance 6 to destination D, while B advertises distance 2 to D. Which route should X select?

26 Router X learned its route to network N from neighbor Y. Under poison reverse, what metric does X advertise for N back to Y?

27 After a link failure, two distance-vector routers repeatedly advertise increasingly larger metrics for an unreachable destination. Which problem is occurring?

28 A router receives two link-state advertisements from the same origin, with sequence numbers 41 and 44. Assuming no sequence-number wraparound, which advertisement should it retain?

29 Routers P and Q have received the same complete set of link-state advertisements. Why can their shortest-path trees still be different?

30 An IPv4 packet has an Internet Header Length (IHL) value of 7. How many bytes are in its header?

31 An IPv4 datagram has a total length of 4000 bytes, including a 20-byte header. It crosses a link with an MTU of 1500 bytes. Assuming no options, what are the fragment offset and MF flag of the third fragment?

32 When an IPv4 router forwards a packet normally, which header-related action must it perform?

33 A 2000-byte IPv4 datagram with the DF flag set reaches a router whose outgoing link has an MTU of 1500 bytes. What should the router do?

34 Which statement correctly compares the IPv6 base header with the IPv4 header?

35 An IPv6 packet's Payload Length field contains 1200. If no jumbo payload option is used, what is the packet's total length?

36 An IPv6 router receives a packet that is larger than the MTU of the next link. What is the expected behavior?

37 Using RFC 5952 canonical formatting, which is the preferred representation of 2001:0db8:0000:0000:00ab:0000:0000:0010?

38 An organization receives the IPv6 prefix 2001:db8:5a00::/48 and assigns /64 prefixes to its LANs. How many distinct /64 LAN prefixes are available?

39 A NAT device translates source 10.0.0.5:49152 to 203.0.113.8:62001 for a connection to 198.51.100.20:443. What destination should the server use in its reply?

40 An external host initiates a TCP connection to a NAT router's public address and an unused destination port. No static mapping or port-forwarding rule exists. What normally happens?

41 A router has the following forwarding entries: 0.0.0.0/0 -> R1, 172.16.0.0/12 -> R2, 172.16.128.0/17 -> R3, and 172.16.192.0/18 -> R4. Which next hop is selected for destination 172.16.190.10?

42 A router learns exactly four contiguous routes, 10.24.8.0/24 through 10.24.11.0/24, from the same next hop. Assuming no other routes must be included, what is the most specific single aggregate?

43 An undirected graph has edges S-A:4, S-B:2, B-A:1, A-C:5, B-C:8, B-D:10, A-D:7, and C-D:2. After Dijkstra's algorithm completes from S, which result for node C is correct?

44 A directed graph contains S->A:2, S->B:5, and B->A:-10, with no negative cycle. What happens if standard Dijkstra's algorithm permanently settles A before processing B?

45 Router X has link costs and . Neighbor A advertises distances (D, E) = (3, 2), while B advertises (D, E) = (7, 5). What routes does the Bellman-Ford update select?

46 Routers A, B, and C can all exchange distance vectors. Before destination D fails, B reaches D through A, and C reaches D through B. Why can split horizon with poisoned reverse still fail to stop counting to infinity?

47 A router reboots and originates its link-state advertisement with sequence number 1, while other routers retain its pre-reboot advertisement with sequence number 900. Under simple higher-sequence-number acceptance, what is the main failure mode?

48 During asynchronous link-state convergence, routers R1 and R2 temporarily have different link-state database snapshots. Each computes a valid shortest-path tree from its own snapshot. Which statement is correct?

49 An IPv4 datagram has a 20-byte header and a 4000-byte payload. It crosses a link with MTU 1500, and fragmentation is permitted. Which (payload bytes, fragment offset, MF) sequence is correct?

50 An incoming IPv4 fragment has a 20-byte header, 2000 payload bytes, fragment offset 100, and MF=1. It must cross a link with MTU 620. Which offsets and MF values are produced when it is fragmented again?

51 A router decrements an IPv4 packet's TTL by 1. The old header checksum is 0xB861, and no other header field changes. Ignoring an end-around carry that is not needed for these values, what is the new checksum?

52 An IPv4 packet has IHL=11 and Total Length=60. Assuming the header is valid, how many bytes are occupied by options and payload?

53 An IPv6 packet contains the 40-byte base header, an 8-byte Hop-by-Hop Options header, a 20-byte TCP header, and 1200 bytes of application data. What values describe the packet correctly?

54 An IPv6 packet uses Hop-by-Hop Options, Routing, Fragment, and Authentication headers before TCP. Which ordering follows the standard extension-header processing order?

55 Using modified EUI-64, what IPv6 address is formed from prefix 2001:db8:abcd:12::/64 and MAC address 00-1A-2B-3C-4D-5E?

56 What solicited-node multicast address corresponds to unicast address 2001:db8::1234:5678?

57 An organization subdivides 2001:db8:1200::/48 into /56 prefixes. If subnet IDs are numbered from 0, which prefix represents subnet ID 173?

58 Four internal hosts simultaneously open TCP connections using source port 50000 to the same destination IP address and destination port. A PAT device uses one public IPv4 address. What is the minimum number of distinct public source ports required for these connections?

59 An IPv4 NAT receives fragments of a TCP packet. Only the first fragment contains the TCP source and destination ports. How can the NAT consistently translate the later fragments?

60 A host sends an IPv4 packet protected by IPsec Authentication Header through a NAT that changes the source address. No NAT-aware encapsulation is used. What is the expected result?