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Question 1. Which IP address range is reserved for IPv4 multicast traffic? A) 224.0.0.0 – 239.255.255. B) 240.0.0.0 – 255.255.255. C) 192.168.0.0 – 192.168.255. D) 10.0.0.0 – 10.255.255. Answer: A Explanation: Class D addresses from 224.0.0.0 to 239.255.255.255 are defined for multicast. Question 2. What is the purpose of the Reverse Path Forwarding (RPF) check in multicast routing? A) To encrypt multicast packets B) To prevent loops and ensure the packet arrives on the best‑path interface C) To assign VLAN IDs to multicast streams D) To convert multicast to unicast Answer: B Explanation: RPF verifies that a received multicast packet arrived on the interface that the router would use to send traffic back to the source, thus preventing loops. Question 3. In IGMPv2, which message is introduced to speed up group leave processing? A) Membership Query B) Membership Report C) Leave Group D) General Query
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Answer: C Explanation: IGMPv2 adds the Leave Group message, allowing a host to inform the router that it is leaving a multicast group immediately. Question 4. Which Ethernet MAC address prefix is used to map IPv4 multicast addresses? A) 01:00:5E B) 33:33: C) 00:1A:2B D) FF:FF:FF Answer: A Explanation: IPv4 multicast addresses are mapped to MAC addresses with the prefix 01:00:5E, followed by the lower 23 bits of the IP address. Question 5. What is the primary advantage of Source Specific Multicast (SSM) over Any‑Source Multicast (ASM)? A) Requires a Rendezvous Point (RP) B) Allows receivers to specify the exact source, eliminating the need for an RP C) Supports unlimited group addresses D) Enables multicast over IPv6 only Answer: B Explanation: In SSM, receivers join (S,G) directly, so no shared tree or RP is needed, simplifying the architecture and improving security. Question 6. Which address block is allocated for SSM in IPv4?
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Answer: A Explanation: When a source starts sending, the DR encapsulates the first packets in a PIM Register message toward the RP. Question 9. What triggers a switch from the shared (,G) tree to a source‑specific (S,G) tree in PIM‑SM?* A) Receipt of a Prune message from the RP B) The SPT threshold being met (e.g., data rate exceeds configured limit) C) A change in VLAN ID D) The router’s CPU usage exceeds 90 % Answer: B Explanation: When traffic volume exceeds the SPT threshold, routers switch to the shortest‑path tree for efficiency. Question 10. Which IGMP version introduced support for Source Specific Multicast (SSM)? A) IGMPv B) IGMPv C) IGMPv D) IGMPv Answer: C Explanation: IGMPv3 adds the ability to specify source filters, enabling SSM joins. Question 11. In a multi‑access LAN, which router is elected as the Designated Router (DR) for PIM?
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A) The router with the highest IP address B) The router with the lowest priority value C) The router that first sends a PIM Hello with the highest priority (or highest IP if tie) D) The router that receives the most IGMP reports Answer: C Explanation: PIM DR election uses the priority field in Hello messages; the highest priority wins, with IP address as tie‑breaker. Question 12. Which of the following is a link‑local multicast address? A) 224.0.0. B) 225.1.2. C) 232.1.1. D) 239.255.255. Answer: A Explanation: Addresses in 224.0.0.0/24 are link‑local; 224.0.0.5 is used by OSPF. Question 13. What is the primary function of IGMP snooping on a Layer‑2 switch? A) To convert multicast to unicast traffic B) To learn which ports have members of a multicast group and forward only to those ports C) To assign IP addresses to hosts automatically D) To encrypt multicast streams Answer: B
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B) MRIB (Multicast Routing Information Base) C) ARP table D) CAM table Answer: B Explanation: MRIB stores multicast routes, while MFIB contains the actual forwarding entries derived from MRIB. Question 17. What does the PIM “Register‑Stop” message indicate? A) The RP no longer wants to receive registers for a particular (S,G) B) The source has stopped sending traffic C) The DR has lost its neighbor adjacency D) The router is shutting down Answer: A Explanation: Register‑Stop tells the first‑hop router to stop encapsulating packets for that (S,G) because the RP has already received the data. Question 18. Which of the following is a valid reason for an RPF failure on a multicast router? A) The router’s clock is unsynchronized B) Asymmetric unicast routing causing the incoming interface not to match the RPF lookup C) The multicast group address is not in the SSM range D) The VLAN tag is missing Answer: B
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Explanation: RPF failures occur when the packet arrives on an interface that is not the one the router would use to reach the source according to its unicast routing table. Question 19. In MSDP, what type of message advertises an active source to remote peers? A) SA (Source‑Active) message B) RP‑Announcement C) PIM‑Join D) IGMP‑Leave Answer: A Explanation: SA messages carry (S,G) information from one RP to another across domains. Question 20. Which protocol is used to carry MSDP messages between RPs? A) UDP port 521 B) TCP port 639 C) SCTP port 3868 D) ICMP Answer: B Explanation: MSDP uses TCP port 639 for reliable transport of SA messages. Question 21. In an Alcatel‑Lucent VPRN, which routing table is consulted for the RPF check of multicast traffic? A) Global unicast table only B) The VRF‑specific unicast routing table (VRF‑aware RPF) C) The MPLS LDP table
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A) Multiple RPs share the same IP address, providing redundancy and load‑sharing. B) An RP that can also act as a source. C) An RP that only serves SSM groups. D) An RP that uses broadcast to announce its presence. Answer: A Explanation: Anycast RP uses the same IP address advertised in the IGP, enabling multiple routers to serve as the RP for the same group. Question 25. In a PIM‑SM domain, what does the “(,G) Join” message represent?* A) A request to join the source‑specific tree. B) A request to join the shared tree rooted at the RP for group G. C) A request to prune traffic from group G. D) A request to become the DR for group G. Answer: B Explanation: (*,G) Join builds the shared tree toward the RP for the specified group. Question 26. Which IGMP query type is sent by a router to verify that there are still listeners for a specific group? A) General Query B) Group‑Specific Query C) Membership Report D) Leave Group Answer: B
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Explanation: Group‑Specific Queries target a single multicast group to confirm active receivers. Question 27. What is the default multicast MAC address for the IPv4 address 224.0.0.22? A) 01:00:5E:00:00: B) 01:00:5E:00:00: C) 33:33:00:00:00: D) 01:00:5E:00:00:0A Answer: A Explanation: The lower 23 bits of 224.0.0.22 (0x000016) are placed after the 01:00:5E prefix, resulting in 01:00:5E:00:00:16. Question 28. Which of the following statements about IGMPv3 “Exclude” mode is correct? A) It allows a host to receive traffic from all sources except those listed. B) It limits traffic to a single source only. C) It disables all multicast traffic on the interface. D) It forces the router to act as an RP. Answer: A Explanation: IGMPv3 “Exclude” mode lets a receiver specify sources to block while receiving from all others. Question 29. In an Alcatel‑Lucent router, which command displays the current PIM neighbor relationships? A) show pim neighbor B) display pim peers
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Question 32. In a PIM‑SSM deployment, what happens if a receiver sends an IGMPv2 join to a group in the 232.0.0.0/8 range? A) The router will reject the join because IGMPv2 does not support source filters. B) The router will map the IGMPv2 join to an SSM (S,G) join using a default source. C) The router will treat it as an ASM join and require an RP. D) The join will be silently ignored. Answer: B Explanation: Many implementations map IGMPv2 joins for SSM groups to a default source, allowing compatibility. Question 33. Which of the following is NOT a characteristic of a “Sparse” multicast environment? A) Receivers are widely dispersed. B) Most subnets do not have members of a given group. C) Multicast traffic is flooded everywhere. D) A shared tree with an RP is used initially. Answer: C Explanation: Sparse mode avoids flooding; it builds trees only where receivers exist. Question 34. What does the “Register‑Stop” timer control on a first‑hop router? A) How long the router waits before sending a Register after seeing the first packet. B) The interval between successive Register messages for the same (S,G). C) The time after which the router stops sending Registers if no data is received from the source. D) The duration the RP holds a (S,G) entry after a Prune.
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Answer: C Explanation: The Register‑Stop timer defines how long the DR will continue sending Registers after receiving a Register‑Stop from the RP. Question 35. Which PIM message is used to prune a branch of the shared tree that no longer needs traffic? A) Prune B) Register C) Join D) Assert Answer: A Explanation: Prune messages tell downstream routers to stop forwarding (*,G) traffic on that interface. Question 36. In Alcatel‑Lucent terminology, what does “MVPN Profile 0 ” refer to? A) A multicast VPN that runs PIM over PIM (no BGP). B) A VPN that only supports IGMPv1. C) A unicast‑only VPN. D) A VPN that uses static RP only. Answer: A Explanation: Profile 0 implements multicast VPN by running PIM inside each VRF and across the provider network, without BGP.
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D) 224.0.0.
Answer: D Explanation: PIM uses 224.0.0.9 for its hello and other control messages. Question 40. In the context of multicast, what does “ASM” stand for? A) Automatic Source Mapping B) Any‑Source Multicast C) Active Source Management D) Address Specific Multicast Answer: B Explanation: ASM denotes Any‑Source Multicast, where receivers can receive traffic from any source sending to the group. Question 41. Which command would you use to verify the multicast forwarding table (MFIB) on an Alcatel‑Lucent router? A) show mfib B) display multicast forwarding C) show multicast mfib D) show ip mfib Answer: C Explanation: The show multicast mfib command displays the MFIB entries. Question 42. What is the main reason to use a “Limited‑Scope” multicast address range?
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A) To limit the TTL to a single hop. B) To restrict the distribution of the group to a specific domain or site. C) To enable encryption on the group. D) To allow the group to be used for IPv6 only. Answer: B Explanation: Limited‑Scope addresses (e.g., 239.0.0.0/8) are intended for use within an organization, preventing accidental global propagation. Question 43. Which of the following statements about “PIM‑Sparse‑Mode” is FALSE? A) It requires an RP for each multicast group. B) It builds a shared tree first, then may switch to a source tree. C) It floods multicast traffic to all interfaces by default. D) It relies on the unicast routing table for RPF checks. Answer: C Explanation: PIM‑SM does NOT flood traffic; it builds trees only where needed. Question 44. In an MSDP peering, what determines the TCP connection’s directionality? A) The router with the higher IP address initiates the connection. B) The router with the higher BSR priority initiates. C) The RP with the higher AS number initiates. D) The router with the lower IP address initiates. Answer: D
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C) To indicate that a source has stopped sending. D) To synchronize timers between routers. Answer: A Explanation: Assert messages are used on multi‑access networks to elect the forwarder for a particular (S,G) when multiple routers could forward. Question 48. Which multicast address is reserved for “All Hosts” on a local network segment? A) 224.0.0. B) 224.0.0. C) 224.0.0. D) 224.0.0. Answer: A Explanation: 224.0.0.1 is the “All Hosts” group, received by every IPv4 multicast‑capable host on the local network. Question 49. In Alcatel‑Lucent routers, what does the command multicast routing enable? A) Global multicast forwarding and the MRIB/MFIB creation. B) Only IGMP on interfaces. C) Only PIM on interfaces. D) Static RP configuration. Answer: A
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Explanation: multicast routing activates the multicast subsystem globally, allowing MRIB/MFIB to be built. Question 50. Which of the following best describes the “Source‑Active (SA)” message in MSDP? A) It carries a list of (S,G) entries from one RP to another. B) It advertises a new RP election. C) It signals a source shutdown. D) It synchronizes timers between MSDP peers. Answer: A Explanation: SA messages contain active source information for a specific group, enabling other domains to join the source. Question 51. Which of the following is a reason to prefer SSM over ASM for video streaming? A) SSM removes the need for an RP, reducing latency and simplifying the tree. B) SSM allows any source to inject traffic into the group. C) SSM supports larger group address spaces. D) SSM enables multicast over UDP only. Answer: A Explanation: SSM’s (S,G) model eliminates the shared tree and RP, providing faster convergence and better security for controlled video streams. Question 52. What is the default TTL value for most link‑local multicast packets (e.g., 224.0.0.x)?
