2013 Latest Cisco 350-001 Exam Section 2: Addressing (7 Questions)
QUESTION NO: 1
How are Layer 3 multicast IP addresses mapped to Token Ring MAC addresses? (Choose all that apply).
A. All IP Multicast addresses are mapped to broadcast MAC address FFFF.FFFF.FFFF.
B. All IP Multicast addresses are mapped to network MAC address 0000.0000.0000.
C. All IP Multicast addresses are mapped to Functional Address C000.0004.0000.
D. In the same method as is used in Ethernet networks.
E. Token ring MAC addresses are not mapped to IP multicast addresses.
Answer: A, C
By default, IP multicast datagrams on Token Ring LAN segments used the MAC-level broadcast address 0xFFFF.FFFF.FFFF. That places an unnecessary burden on all devices that do not participate in IP multicast. The IP multicast over Token Ring LANs feature defines a way to map IP multicast addresses to a single Token Ring MAC address.
This feature defines the Token Ring functional address (0xc000.0004.0000) that should be used over Token Ring. A functional address is a severely restricted form of multicast addressing implemented on Token Ring interfaces. Only 31 functional addresses are available. A bit in the destination MAC address designates it as a functional address. The implementation used by Cisco Systems complies withRFC 1469, IP Multicast over Token-Ring Local Area Networks. Reference: See RFC 1469, IP Multicast over Token-Ring Local Area Networks Also see http://www.cisco.com/univercd/cc/td/doc/product/software/ios113ed/113ed_cr/np1_c/1cmulti.htm#21101
QUESTION NO: 2 The IANA owns a block of Ethernet MAC address that start with 01:00:5E in haxadecimal formal. Half of this block is allocated for multicast addresses. The range from 0100.5e00.0000 through 0100.5e7f.ffff is the available range of Ethernet MAC address for IP multicast. This allocation allow for 23 bits in the Ethernet address to correspond to the IP multicast group address. The mapping places the lower 23 bits of the IP multicast group address into these available 23 bits in the Ethernet address. Because the upper five bits of the IP multicast address are dropped in this mapping, the resulting address in not unique. In fact, 32 different multicast group IDs map to the same Ethernet address.
188.8.131.52 and 184.108.40.206 have been assigned to map to the same multicast MAC address on a Layer 2 switch. What will occur?
A. If one user is subscribed to Group A (as designated by 220.127.116.11) and the other user is subscribed to Group B (as designated by 18.104.22.168), they would both receive only the streams meant for them. Group A would go to 22.214.171.124 and group B would go to
B. If one user is subscribed to Group A (as designated by 126.96.36.199) and the other user is subscribed to Group B (as designated by 188.8.131.52), they would both receive only the first stream that reached the network.
C. If one user is subscribed to Group A (as designated by 184.108.40.206) and the other user is subscribed to Group B (as designated by 220.127.116.11), they would both receive both streams, A and B streams.
D. If one user is subscribed to Group A (as designated by 18.104.22.168) and the other user is subscribed to Group B (as designated by 22.214.171.124), both of them would not receive A and B streams.
E. None of the above
Although mathematically there are 32 possibilities for overlap of addresses it is very unlikely to happen in real life. If it does, the impact is that another set of stations receives the multicast traffic. This is still far preferable to ALL stations receiving the traffic. This is always the case where two IP multicast addresses share the same MAC address.
QUESTION NO: 3
Which IP address maps to the Ethernet multicast MAC address of 01-00-5e-10-20-02? (Choose all that apply)
G. All of the above
H. None of the above
Answer: E, F
Ethernet interfaces map the lower 23 bits of the IP multicast address to the lower 23 bits of the MAC 0100.5e00.0000. As an example, the IP multicast address 126.96.36.199 is mapped to the MAC layer as 0100.5e00.0002.
HEX 10 = 00010000 – could be both 16 and 144 (decimal) due to the fact that we
HEX 02 = 00000010 = 2.
QUESTION NO: 4
What is the class D IP address range 188.8.131.52-184.108.40.206 used for?
A. Administratively Scoped multicast traffic meant for internal use.
B. Link-local multicast traffic made up of network control messages meant to stay in the local subnet.
C. Global Internet multicast traffic meant to travel throughout the Internet.
D. Any valid multicast data stream for use with multicast applications.
E. Routing protocol use.
The 239 address range is reserved for IP multicast traffic that is to be used for internal use only. It is similar to RFC 1918 private IP address space, except instead of specifying unicast address ranges it specifies multicast.
B, E. Link level multicast messages, such as those used by routing protocols, use the
220.127.116.11 address range. For example, IGRP uses 18.104.22.168 and OSPF uses 22.214.171.124
C, D. This address range should never be seen in the Internet. It is reserved for private use
Jeff Doyle Volume II chapter on IP Multicast.
QUESTION NO: 5
You wish to implement a multicast video application over your private, internal network. To do this, you need to use a private multicast range of IP addresses across your network. Which IP range should you use?
A. 126.96.36.199 – 188.8.131.52
B. 184.108.40.206 – 220.127.116.11
C. 241.0.0.0 – 241.255.255.255
D. 18.104.22.168 – 22.214.171.124
E. 240.0.0.0 – 254.255.255.255.
The reserved, administratively scoped IPv4 multicast address space is defined to be the range 126.96.36.199 to 188.8.131.52. Administratively scoped multicast addresses are for use only on a private network and are not to be used on the Internet.
RFC 2365 – http://www.faqs.org/rfcs/rfc2365.html
QUESTION NO: 6 The TestKing network is using IP multicast within to conserve bandwidth during the training video seminars. In this IP multicast network, which of the following correctly describes scoping?
A. Scoping is the restriction of multicast data transport to certain limited regions of the network. There are two types: TTL scoping and administrative scoping.
B. Scoping is used by SSM to locate the sources and receivers in certain limited regions of the network. There are two types: TTL scoping and administrative scoping.
C. Scoping is a process used in MSDP to locate the sources and receivers in different AS.
D. PIM dense mode uses scoping to locate the sources and receivers in order to built shared trees.
Traditionally, IP multicast uses a Time to Live (TTL) parameter in an IP multicast application and multicast routers to control the multicast distribution. When you define the TTL value in an IP multicast application, contents don’t transmit beyond the TTL value. For example, if you set Site Server’s Active Channel Multicaster TTL value to 10, you ensure that Site Server’s Web contents don’t multicast beyond 10 router hops. Each multicast packet carries a TTL value in its IP header. Just as in unicast, every time a multicast router forwards a multicast packet, the router decreases the packet’s TTL by 1. As an alternative to TTL scoping, the Internet Engineering Task Force (IETF) proposed Administratively Scoped IP Multicast as an Internet standard in its Request for Comments (RFC) 2365 in July 1998. Administrative scoping lets you scope a multicast to a certain network boundary (e.g., within your organization) by using an administratively scoped address. IETF has designated IP multicast addresses between 184.108.40.206 and
220.127.116.11 as administratively scoped addresses for local use in intranets. You can configure routers that support administratively scoped addressing on the border of your network to confine your private multicast region. You can also define multiple isolated multicast regions in your network so that sensitive multicast data will travel only within a designated area.
QUESTION NO: 7
The TestKing network is implementing IP multicast and they want to ensure that the IP addresses they used are contained within the TestKing autonomous system. What is the range of limited scope/administrative scope addresses that should be used?
A. Addresses in the 18.104.22.168/8 range
B. Addresses in the 22.214.171.124/8 range
C. Addresses in the 126.96.36.199/8 range
D. Addresses in the 188.8.131.52/8 range
E. Addresses in the 184.108.40.206/8 range
F. None of the above
Explanation The range of addresses from 220.127.116.11 through 18.104.22.168 contains limited scope addresses or administratively scoped addresses. These are defined by RFC 2365 to be constrained to a local group or organization. Routers are typically configured with filters to prevent multicast traffic in this address range from flowing outside an autonomous system (AS) or any user-defined domain. Within an autonomous system or domain, the limited scope address range can be further subdivided so those local multicast boundaries can be defined. This also allows for address reuse among these smaller domains. These addresses are the IP multicast version of the private, RFC 1918, addresses used for unicast. Reference:http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/ipmulti.htm
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