Implement multicast forwarding

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These questions are derived from the Self Test Software Practice Test for Cisco exam #642-901 – Building Scalable Cisco Internetworks

Objective: Implement multicast forwarding
SubObjective: Describe IP Multicast (e.g., Layer-3 to Layer-2 mapping, IGMP, etc.)

Single Answer, Multiple Choice

Which of the following steps will a host take to leave a multicast group when IGMPv1 is used on a network?

  1. The host will send a leave message to 224.0.0.2.
  2. The host will send a membership query to 224.0.0.1.
  3. The host will send a membership report to 224.0.0.2.
  4. The host will leave the group quietly without sending an IGMP message.

Answer:
D. The host will leave the group quietly without sending an IGMP message.

Tutorial:
When Internet Group Management Protocol version 1 (IGMPv1) is used on a network, the host will leave the multicast group quietly without sending an IGMP message. IGMPv1 does not have any mechanism for hosts to leave a multicast group. If a host is the last member of a multicast group, then the multicast querier router will eventually discover that no hosts from that group are responding to its membership queries and remove that group from the multicast tree.

When IGMP version 2 (IGMPv2) is used on a network, the host will send a leave message to 224.0.0.2 in order to leave a multicast group; the address 224.0.0.2 is the all-routers multicast address. Leave reports are only available with IGMPv2.

Membership queries are sent to the all-hosts multicast address, 224.0.0.1, to discover which groups contain multicast members. Membership reports are sent to the all-routers multicast address, 224.0.0.2, when hosts join a multicast group.

Reference:
BCMSN Student Guide v2.0 – Examining Cisco AVVID Services and Applications – IGMP and CGMP Operation

Cisco Documentation Web Site, IP Multicast Technology Overview, Intradomain Routing Protocols, Internet Group Management Protocol (IGMP), IGMP Version 1.

http://www.cisco.com/univercd/cc/td/doc/cisintwk/intsolns/mcst_sol/mcst_ovr.htm#xtocid12

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