2013 Latest Cisco 350-001 Exam Section 1: IGMP/CGMP (5 Questions)
QUESTION NO: 1
Part of the Testking IP multicast network is shown below: H1, H2, H3, and rtr-a are all IGMP version 2 devices. Host 2 and Host 3 belong to the
184.108.40.206 group. After a while, H2 sends out an IGMPv2 Leave message to leave the
220.127.116.11 group. How will rtr-a react to this leave message?
A. It will send an IGMPv2 Query to the all multicast hosts address 18.104.22.168.
B. It will send an IGMPv2 Group Specific Query to 22.214.171.124
C. It will send an IGMPv2 Leave Acknowledgement to Hosts H1 and H3.
D. It will send an IGMPv2 General Query to 126.96.36.199
E. It will send an IGMPv2 Group Specific Query to 188.8.131.52.
In IGMP version 2, a Leave message is responded by a group specific query from the router to check if there are any additional hosts participating in the multicast session. The group specific query is always destined for the multicast address that is being used.
A. The address 184.108.40.206 would never be used in this situation. In fact, the notion of a multicast “broadcast” does not exist.
C. Lave messages are not acknowledged.
D. General Query messages are not used.
E. The group specific query is always destined for the multicast address that is being used, which is 220.127.116.11 in this case.
QUESTION NO: 2
The TestKing network has a mix of IGMP version 1 and version 2 devices in its IP multicast network as shown below: H1 and H2 are both IGMPv2 speakers and are also members of group 18.104.22.168. H3 is an IGMPv1 speaker and sends an IGMPv1 Membership Report to join group 22.214.171.124.
What will happen?
A. The router rtr-a will do nothing, since there are already members of group 126.96.36.199 on the subnet.
B. The router rtr-a will ignore all IGMPv2 Leave messages while the IGMPv1 host is a member of group 188.8.131.52.
C. The router rtr-a will stop sending IGMPv2 Group-Specific queries in response to IGMPv1 Leaves received on this subnet for groups 184.108.40.206, while the IGMPv1 hosts is a member of group 220.127.116.11.
D. The router rtr-a will ignore the IGMPv1 Membership Report because router rtr-a is an IGMPv2 speaker and IGMPv1 are not compatible.
With IGMP version 1 and version 2 on the same network, routers will revert to v1, so the router will ignore the leave requests from all v2 members as long as the v1 member is still active for that multicast session.
A. Although there are already members on the same segment, the routers must be aware
of the fact that there are a mix of v1 and v2 devices, so that the v2 leave messages can be
C. When the v1 device leaves the multicast session, the router must still send the group
query out to see if the v2 devices are also still actively participating in the multicast
D. IGMP version 2 was designed to be backward compatible with version 1.
“CCIE Professional Development Routing TCP/IP Volume II” by Jeff Doyle and Jennifer
De Haven Carroll, Page 414.
QUESTION NO: 3 IGMP is used to dynamically register individual hosts in a multicast group on a particular LAN. Hosts identify group memberships by sending IGMP messages to their local multicast router. Under IGMP, routers listen to IGMP messages and periodically send out queries to discover which groups are active or inactive on a particular subnet. Hosts need to actively communicate to the local multicast router that they intend to leave a group. If there are no replies, the router rimes out the group and stops forwarding the traffic. In order for this to work, what needs to be implemented?
The Internet Group Management Protocol (IGMP) is used by IP hosts to report their host group memberships to any immediately neighboring multicast routers. IGMP messages are encapsulated in IP datagrams, with an IP protocol number of 2. IGMP has versions IGMP v1, v2 and v3. In IGMPv2, leave messages were added to the protocol. This allowed group membership termination to be quickly reported to the routing protocol, which is important for high-bandwidth multicast groups and/or subnets with highly volatile group membership.
A. IGMPv1: Hosts can join multicast groups. There were no leave messages. Routers were using a time-out based mechanism to discover the groups that are of no interest to the members.
C. IGMPv3: Major revision of the protocol. It allows hosts to specify the list of hosts from which they want to receive traffic from. Traffic from other hosts is blocked inside the network. It also allows hosts to block inside the network packetsthat come from sources that sent unwanted traffic.
D. IGMPv4 is not yet in use.
E. CGMP is the Cisco Group Management Protocol (CGMP) which is a multicast protocol used by Cisco LAN switches, and not routers.
QUESTION NO: 4 In the TestKing network, hosts need to actively communicate to the local multicast router that they intend to leave a group. The router then sends out a group-specific query and determines if any remaining hosts are interested in receiving the traffic. If there are no replies, the router times out the group and stops forwarding the traffic. In order for this to work, what needs to be implemented?
C. IGMP snooping
IGMP version 2 is the Industry-standard protocol for managing multicast group membership, including support for IGMP-leave messages and group-specific queries. Leave Group message is a new type different from IGMP version 1. Membership Report is issued by host that want to join a specific multicast group (GDA). When IGMP router receive the Membership Report, it will add the GDA to the multicast routing table and start forwarding the IGMP traffic to this group. Membership Queries are issued by router at regular intervals to check whether there is still a host interested in the GDA in that segment. Host Membership Reports are sent either when the host wants to receive GDA traffic or response for a membership query from IGMP router.
If a host does not want to receive the IGMP traffic any more, it sends a Leave Group message. When the multicast router receives this Leave Group message, it removes the GDA from the multicast routing table. In addition, IGMP multicast routers periodically send Host Membership Query messages (hereinafter called Queries) to discover which host groups have members on their attached local networks.If no Reports are received for a particular group after some number of Queries, the routers assume that that group has no local members and that they need not forward remotely-originated multicasts for that group onto the local network. In addition, IGMP version 2 has leave mechanisms.
A. In IGMP version 1, hosts can join multicast groups. There were no leave messages.
Routers were using a time-out based mechanism to discover the groups that are of no
interest to the members.
D, F. These are incorrect terms for this IP multicasting functionality.
E. CGMP is used between Cisco switches and routers to provide for IP multicast
information to be passed between the two.
QUESTION NO: 5 The default behaviour for a Layer 2 switch is to forward all multicast traffic to every port that belongs to the destination LAN on the switch. This behavior reduces the efficiency of the switch, whose purpose is to limit traffic to the ports that need to receive the data. In an effort to increase the efficiency of the TestKing network, you wish to utilize different protocols on the LAN.
Choose the correct protocols to handle IP multicast efficiently in the TestKing layer 2 switched IP network. (Select the best choice).
A. Use Router-Port Group Mangement Protocol (RGMP) on subnets that include end users or receiver clients. Use Cisco Group Management Protocol (CGMP), IGMP Snooping on routed segments that contain only routers, such as in a collapsed backbone.
B. Use Router-Port Group Mangement Protocol (RGMP) on subnets that include end users or receiver clients and routes segments that contain only routers, such as in a collapsed backbone.
C. Use Cisco Group Management Protocol (CGMP), IGMP Snooping on subnets that include end users or receiver clients. Use Router-Port Group Management Protocol (RGMP) on routed segments that contain only routers, such as in a collapsed backbone.
D. Use Cisco Group Management Protocol (CGMP) on subnets that include end users or receiver clients and routed segments that contain only routers, such as in a collapsed backbone.
E. Use IGMP Snooping on subnets that include end users or receiver clients and routed segments that contain only routers, such as in a collapsed backbone.
The purpose of Cisco Group Management Protocol (CGMP) and Internet Group Management Protocol (IGMP) snooping is to restrain multicast traffic in a switched network. By default, a LAN switch floods multicast traffic within the broadcast domain. This can consume a lot of bandwidth if many multicast servers are sending streams to the segment. IGMP snooping is a feature that allows the switch to “listen in” on the IGMP conversations between hosts and routers. When a switch hears an IGMP report from a host for a given multicast group, the switch adds the host’s port number to the GDA list for that group. And, when the switch hears an IGMP Leave, it removes the host’s port from the CAM table entry. RGMP constrains multicast traffic that exits the Cisco Router through ports to which only disinterested multicast routers are connected. RGMP reduces network congestion by forwarding multicast traffic to only those routers that are configured to receive it. Note: To use RGMP, you must enable IGMP snooping on the Cisco router. IGMP snooping constrains multicast traffic that exits through LAN ports to which hosts are connected. IGMP snooping does not constrain traffic that exits through LAN ports to which one or more multicast routers are connected.
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