Multicast in IP ( CCNP )

1.By default, what does a router or Layer 3 switch do with multicast packets?

** It drops them because multicast routing is not enabled by default.

2.By default, what does a Layer 2 switch do with a multicast packet?

** It floods the packet out all ports on the source VLAN, as if it were a broadcast packet.

3.What high-order bit combination signals that an IP address is used for multicast?

** 1110

4.If the IP-to-MAC multicast address mapping is somewhat ambiguous, how can a frame be forwarded to the correct destination group?

** The IP header must be examined in addition to the multicast MAC destination address.

5.What IP multicast address range is set aside for use only on the local network segment?

** 224.0.0.0 to 224.0.0.255

6.For the RPF check, the source IP address is looked up in the unicast routing table. To forward the packet, what should the result of the test be?

** The unicast route to the source must be out the interface where the packet arrived.

7.What important difference exists between IGMPv1 and IGMPv2?

** Hosts can request to leave a multicast group immediately with IGMPv2. IGMPv1 doesn't have any mechanism for leaving a group other than an aging-out process.

8.To join a multicast group, what type of message is sent? Where is this message sent?

** An IGMP membership report is sent. The IGMP message is with a destination address of the multicast group itself so that the nearest multicast router will receive it.

9.What is the purpose of the IGMP querier?

** It is a router that periodically asks all hosts if any of them want to join the multicast group. Interested hosts must respond with a membership report.