Ccna certification Practice Tests

351

 70.  C.  The command 

ipv6 address dhcp will configure the interface to obtain its IP address 

via stateful DHCPv6. The command 

ipv6 address dhcp gi 0/0 is incorrect. The 

command 

ipv6 address dhcpv6 is incorrect. The command ipv6 address stateless 

is incorrect.

 71.  C.  When the lease for a node is deleted on the DHCP server, the DHCP server is free 

to hand out the lease to another node. This happens independently from the client, as 

there is no communication from server to client about the lease. The client will retain 

the IP address until the renewal period, which will cause a duplication of IP addressing. 

The client is responsible for the management of the lease cycle; therefore, the server has 

no obligation to contact the client when the lease is deleted. The client will not know to 

contact the server for a renewal of the lease until the halfway point of the lease cycle. If or 

when the server issues the lease to another client, the existing client will still maintain the 

original lease.

 72.  A.  At seven-eighths of the lease cycle, the DHCP client will perform a rebinding. The 

rebinding process means that the original DHCP server was down at the one-half mark 

of the lease, so now the client will try to rebind with any responding DHCP server. The 

DHCP client will retain the lease until the end of the lease cycle. During the rebind the 

DHCP client will attempt to renew a new lease with any DHCP server. The DHCP client 

will not relinquish the IP address until the very end of the lease.

 73.  A.  QoS classifies traffic with access control lists (ACLs) and applies markings to the 

packets. Layer 2 ASICs help process the QoS but do not classify the QoS for traffic. Route 

tables are used for routing and therefore have no effect on QoS. Frame filters are used to 

forward/filter frames to their destination port; they are part of the switching process.

 74.  C.  Jitter is the measurement of variation between consecutive packet times from source to 

destination (one-way delay). For example, if the first packet takes 10 ms and the second, 

third, and fourth take 10 ms, the jitter, or variance, is 0 ms. The simple calculation is an 

average of packet times. However, data size has an influence on jitter, so the more accurate 

calculation is J = J + (D (I – 1 , I) – J) / 16. Bandwidth is the total width of data that can 

be passed for a specific interval. Delay is the measurement of how long a packet takes to 

travel from source to destination. Loss is the total number of packets that are not delivered 

from source to destination.

 75.  B.  The Class of Service (CoS) field (802.1p) is only found in layer 2 transmissions, 

specifically only across trunks due to the dependency of 802.1Q. The CoS field is a 3-bit 

field in the 802.1Q frame type. The CoS field does not need to be present from end to end 

of a transmission because the transmission can traverse a router. The CoS field is a 3-bit 

field, not a 6-bit field.

 76.  D.  Loss is the measurement of discarded packets. The measurement is a percentage 

of transmitted packets. For example, if 100 packets are transmitted and 3 packets are 

dropped, then the loss is 3%. Loss can be attributed to congestion, faulty wiring, EMI, 

or device queue congestion. Bandwidth is the total width of data that can be passed for 

a specific interval. Delay is the measurement of how long a packet takes to travel from 

source to destination. Jitter is the measurement of variation between consecutive packet 

times from source to destination (one-way delay).

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