Practice Chapters 16-20 Flashcards
16.1 Which of the following is a congestion-avoidance mechanism?
A. LMI
B. WRED
C. QPM
D. QoS
B. Dropping packets as they arrive is called tail drop. Selective dropping of packets during the time queues are filling up is called congestion avoidance (CA). Cisco uses weighted random early detection (WRED) as a CA scheme to monitor the buffer depth and performs early discards (drops) on random packets when the minimum defined queue threshold is exceeded.
16.2 Which three features are properties and one-way requirements for voice traffic? (Choose three.)
A. Bursty voice traffic
B. Smooth voice traffic
C. Latency should be below 400ms
D. Latency should be below 150ms
E. Bandwidth is roughly between 30 and 128Kbps
F. Bandwidth is roughly between 0.5 and 20 Mbps
B, D, E. Voice traffic is real-time traffic requiring consistent, predictable bandwidth and packet arrival times. One-way requirements include latency < 150 ms, jitter <30 ms, and loss < 1%. Bandwidth needs to be 30 to 128 Kbps.
16.3 Which statement about QoS trust boundaries or domains is true?
A. The trust boundary is always a router.
B. PCs, printers and tablets are usually part of a trusted domain.
C. An IP phone is a common trust boundary.
D. Routing will not work unless the service provider and the enterprise network are one
single trust domain.
C. A trust boundary is where packets are classified and marked. IP phones and the boundary between the ISP and enterprise network are common examples of trust boundaries.
16.4 Which advanced classification tool can be used to classify data applications?
A. NBAR
B. MPLS
C. APIC-EM
D. ToS
A. NBAR is a layer 4 to layer 7, deep-packet inspection classifier. NBAR is more CPU intensive than marking and uses the existing markings, addresses, or ACLs.
16.5 The DSCP field constitutes how many fields in the IP header?
A. 3 bits
B. 4 bits
C. 6 bits
D. 8 bits
C. DSCP is a set of 6-bit values that are used to describe the meaning of the layer 3 IPv4 ToS field. While IP precedence is the old way to mark ToS, DSCP is the new way and is backward compatible with IP precedence.
16.6 Which option is a layer 2 QoS marking?
A. EXP
B. QoS group
C. DSCP
D. CoS
D. Class of service (CoS) is a term used to describe designated fields in a frame or packet header. How devices treat packets in your network depends on the field values. CoS is usually used with Ethernet frames and contains 3 bits.
16.7 Which QoS mechanism will drop traffic if a session uses more than the allotted bandwidth?
A. Congestion management
B. Shaping
C. Policing
D. Marking
C. When traffic exceeds the allocated rate, the policer can take one of two actions: It can either drop traffic or re-mark it to another class of service. The new class usually has a higher drop probability.
17.1 How is an EUI-64 format interface ID created from a 48-bit MAC address?
A. By appending 0xFF to the MAC address
B. By prefixing the MAC address with 0xFFEE
C. By prefixing the MAC address with 0xFF and appending 0xFF to it
D. By inserting 0xFFFE between the upper 3 bytes and the lower 3 bytes of the MAC address
D. The modified EUI-64 format interface identifier is derived from the 48-bit link-layer (MAC) address by inserting the hexadecimal number FFFE between the upper 3 bytes (OUI field) and the lower 3 bytes (serial number) of the link-layer address.
17.2 Which option is a valid IPv6 address?
A. 2001:0000:130F::099a::12a
B. 2002:7654:A1AD:61:81AF:CCC1
C. FEC0:ABCD:WXYZ:0067::2A4
D. 2004:1:25A4:886F::1
D. An IPv6 address is represented as eight groups of four hexadecimal digits, each group representing 16 bits (two octets). The groups are separated by colons (:). Option A has two double colons, B doesn’t have 8 fields, and option C has invalid hex characters.
17.3 Which three statements about IPv6 prefixes are true? (Choose three.)
A. FF00:/8 is used for IPv6 multicast.
B. FE80::/10 is used for link-local unicast.
C. FC00::/7 is used in private networks.
D. 2001::1/127 is used for loopback addresses.
E. FE80::/8 is used for link-local unicast.
F. FEC0::/10 is used for IPv6 broadcast.
A, B, C. This question is easier to answer if you just take out the wrong options. First, the loopback is only ::1, so that makes option D wrong. Link local is FE80::/10, not /8, and there are no broadcasts.
17.4 What are three approaches that are used when migrating from an IPv4 addressing scheme
to an IPv6 scheme? (Choose three.)
A. Enable dual-stack routing.
B. Configure IPv6 directly.
C. Configure IPv4 tunnels between IPv6 islands.
D. Use proxying and translation to translate IPv6 packets into IPv4 packets.
E. Use DHCPv6 to map IPv4 addresses to IPv6 addresses.
A, C, D. Several methods are used in terms of migration, including tunneling, translators, and dual-stack. Tunnels are used to carry one protocol inside another, while translators simply translate IPv6 packets into IPv4 packets. Dual-stack uses a combination of both native IPv4 and IPv6. With dual-stack, devices are able to run IPv4 and IPv6 together, and if IPv6 communication is possible, that is the preferred protocol. Hosts can simultaneously reach IPv4 and IPv6 content.
17.5 Which two statements about IPv6 router advertisement messages are true? (Choose two.)
A. They use ICMPv6 type 134.
B. The advertised prefix length must be 64 bits.
C. The advertised prefix length must be 48 bits.
D. They are sourced from the configured IPv6 interface address.
E. Their destination is always the link-local address of the neighboring node.
A, B. ICMPv6 router advertisements use type 134 and must be at least 64 bits in length.
17.6 Which of the following is true when describing an IPv6 anycast address? (Choose three.)
A. One-to-many communication model
B. One-to-nearest communication model
C. Any-to-many communication model
D. A unique IPv6 address for each device in the group
E. The same address for multiple devices in the group
F. Delivery of packets to the group interface that is closest to the sending device
B, E, F. Anycast addresses identify multiple interfaces, which is somewhat similar to multicast addresses; however, the big difference is that the anycast packet is only delivered to one address, the first one it finds defined in terms of routing distance. This address can also be called one-to-one-of-many, or one-to-nearest.
17.7 You want to ping the loopback address of your IPv6 local host. What will you type?
A. ping 127.0.0.1
B. ping 0.0.0.0
C. ping ::1
D. trace 0.0.::1
C. The loopback address with IPv4 is 127.0.0.1. With IPv6, that address is ::1.
17.8 What are three features of the IPv6 protocol? (Choose three.)
A. Optional IPsec
B. Autoconfiguration
C. No broadcasts
D. Complicated header
E. Plug-and-play
F. Checksums
B, C, E. An important feature of IPv6 is that it allows the plug-and-play option to the network devices by allowing them to configure themselves independently. It is possible to plug a node into an IPv6 network without requiring any human intervention. IPv6 does not implement traditional IP broadcasts.
17.9 Which two statements describe characteristics of IPv6 unicast addressing? (Choose two.)
A. Global addresses start with 2000::/3.
B. Link-local addresses start with FE00:/12.
C. Link-local addresses start with FF00::/10.
D. There is only one loopback address and it is ::1.
E. If a global address is assigned to an interface, then that is the only allowable address for the interface.
A, D. The loopback address is ::1, link-local starts with FE80::/10, site-local addresses start with FEC0::/10, global addresses start with 2000::/3, and multicast addresses start with FF00::/8.
17.10 A host sends a router solicitation (RS) on the data link. What destination address is sent with this request?
A. FF02::A
B. FF02::9
C. FF02::2
D. FF02::1
E. FF02::5
C. A router solicitation is sent out using the all-routers multicast address of FF02::2. The router can send a router advertisement to all hosts using the FF02::1 multicast address.
18.1 You need to verify the IPv6 ARP cache on a router and see that the state of an entry is REACH. What does REACH mean?
A. The router is reaching out to get the address.
B. The entry is incomplete.
C. The entry has reached the end of life and will be discarded from the table.
D. A positive confirmation has been received by the neighbor and the path to it is functioning correctly.
D. Positive confirmation has been received confirming that the path to the neighbor is functioning correctly. REACH is good!
18.2 What’s the most common cause of interface errors?
A. Speed mismatch
B. Duplex mismatch
C. Buffer overflows
D. Collisions between a dedicated switch port and an NIC
B. The most common cause of interface errors is a mismatched duplex mode between two ends of an Ethernet link. If they have mismatched duplex settings, you’ll receive a legion of errors, which cause ugly slow performance issues, intermittent connectivity, and massive collisions—even total loss of communication!
18.3 Which command will verify the DTP status on a switch interface?
A. sh dtp status
B. sh dtp status interface interface
C. sh interface interface dtp
D. sh dtp interface interface
D. You can verify the DTP status of an interface with the sh dtp interface interface command.
18.4 What mode will not allow DTP frames generated from a switch port?
A. Nonegotiate
B. Trunk
C. Access
D. Auto
A. No DTP frames are generated from the interface. Nonegotiate can be used only if the neighbor interface is manually set as trunk or access.
18.5 The following output was generated by which command?
IPv6 Address Age Link-layer Addr State Interface
FE80::21A:6DFF:FE64:9B3 0 001a.6c46.9b09 DELAY Fa0/1
2001:DB8:3C4D:2:21A:6DFF:FE64:9B3 0 001a.6c46.9b09 REACH Fa0/1
A. show ip arp
B. show ipv6 arp
C. show ip neighbors
D. show ipv6 neighbors
D. The command show ipv6 neighbors provides the ARP cache on a router.
18.6 Which of the following states tells you that an interface has not communicated within the
neighbor-reachable time frame?
A. REACH
B. STALE
C. TIMEOUT
D. CLEARED
B. The state is STALE when the interface has not communicated within the neighbor-reachable time frame. The next time the neighbor communicates, the state will change back to REACH.
18.7 You receive a call from a user who says that they can’t log in to a remote server, which only runs IPv6. Based on the output, what could the problem be?
C:\Users\Todd Lammle>ipconfig
Connection-specific DNS Suffix . : localdomain
IPv6 Address. . . . . . . . . . . : 2001:db8:3c4d:3:ac3b:2ef:1823:8938
Temporary IPv6 Address. . . . . . : 2001:db8:3c4d:3:2f33:44dd:211:1c3d
Link-local IPv6 Address . . . . . : fe80::ac3b:2ef:1823:8938%11
IPv4 Address. . . . . . . . . . . : 10.1.1.10
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 10.1.1.1
A. The global address is in the wrong subnet.
B. The IPv6 default gateway hasn’t been configured or received from the router.
C. The link-local address hasn’t been resolved, so the host cannot communicate to the router.
D. There are two IPv6 global addresses configured. One must be removed from the configuration.
B. There is no IPv6 default gateway, which will be the link-local address of the router interface, sent to the host as a router advertisement. Until this host receives the router address, the host will communicate with IPv6 only on the local subnet.
18.8. Your host cannot reach remote networks. Based on the output, what’s the problem?
C:\Users\Server1>ipconfig
Windows IP Configuration
Ethernet adapter Local Area Connection:
Connection-specific DNS Suffix . : localdomain
Link-local IPv6 Address . . . . . : fe80::7723:76a2:e73c:2acb%11
IPv4 Address. . . . . . . . . . . : 172.16.20.254
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 172.16.2.1
A. The link-local IPv6 address is wrong.
B. The IPv6 global address is missing.
C. There is no DNS server configuration.
D. The IPv4 default gateway address is misconfigured.
D. This host is using IPv4 to communicate on the network, and without an IPv6 global address, the host will be able to communicate to only remote networks with IPv4. The IPv4 address and default gateway are not configured into the same subnet.
18.9 Which two commands will show you if you have a native VLAN mismatch?
A. show interface native vlan
B. show interface trunk
C. show interface interface switchport
D. show switchport interface
B, C. The commands show interface trunk and show interface interface switchport will show you statistics of ports, which includes native VLAN information.
18.10 You connect two new Cisco 3560 switches together and expect them to use DTP and create
a trunk. But, when you check statistics, you find that they are access ports and didn’t negotiate. Why didn’t DTP work on these Cisco switches?
A. The ports on each side of the link are set to auto trunking.
B. The ports on each side of the link are set to on.
C. The ports on each side of the link are set to dynamic.
D. The ports on each side of the link are set to desirable.
A. Most Cisco switches ship with a default port mode of auto, meaning that they will automatically trunk if they connect to a port that is on or desirable. Remember that not all switches are shipped as mode auto, but many are, and you need to set one side to either on
or desirable in order to trunk between switches.
