CertificationZone

Date of Issue: 05-01-2023

Question 1.
A new workstation is added to a network. The client software is reporting that the Ethernet MAC address of the NIC is the same as a MAC address elsewhere on the network. What best describes this situation?

a) This is not a problem. The message is informational only.
b) This is a problem. MAC addresses on different networks must be unique.
c) This is a problem. MAC addresses must be unique within a network infrastructure regardless of network or LAN segment.
d) This is a problem. MAC addresses within the same network segment must be unique.
e) This is a problem. All activity on the network is suspended by all nodes until the duplicate MAC address issue has been resolved.

Answer

Question 2.
You have installed a new 10/100 Mbps Ethernet network card into a workstation. The workstation had previously been connected to a 10 Mbps hub. The workstation will use the same hub port to connect to the network.

The end-user working at the workstation is now complaining that the network is extremely slow to respond. Since nothing has changed in the network, other than the network interface card, what is the most likely cause of the decrease in network performance?

a) There has been a significant increase in network traffic with the addition of the new network card.
b) The network card has been set to default to 100 Mbps.
c) The network card has been set to default to half-duplex.
d) The network card has been set to full-duplex.
e) The network card has been set to auto-negotiate.

Answer

Question 3.
Switched networks have several benefits over shared media networks. Identify the benefits.

a) Switched networks offer a higher degree of security than shared media networks.
b) Switched network devices switch all frames to all ports; all frames propagate the entire network. Shared media network devices forward frames to only the destination end devices.
c) Switched networks are manageable; whereas shared media networks are not.
d) Switched networks provide more bandwidth per user than shared networks.
e) Switched networks have no benefits over shared media networks.

Answer

Answers

Answer
d) This is a problem. MAC addresses within the same network segment must be unique.

Explanation
MAC addresses (also known as layer 2 addresses) are used to transport frames within a network segment and must be unique within an Ethernet LAN segment. Layer 3 addresses are used when transporting packets between network segments.
[3098]

CCIE Topic(s):
CCIE Objective(s):
CCNA Topic(s): g
CCNA Objective(s): g15

Answer
d) The network card has been set to full-duplex.

Explanation
A network card set to full-duplex when using a hub will, in fact, function, but the duplex mismatch creates issues within the network because the collision detection mechanism is disabled.

A full-duplex network card is unable to detect its frames that have collided on the shared-media segment. Error detection and retransmission of corrupted frames is left to the higher layer protocols. It is this delay in the detection of collisions that is responsible for the end-user's perception of network performance degradation.

It's not uncommon to find network cards set to full-duplex Ethernet when the end-workstation is connected to a hub. This is often the case when network cards are installed by technicians who don't understand full-duplex, or how it operates -- they just know that they want the best performance from the card and set all available options hoping to improve performance.

The alternative answers are not plausible because:

- if a 10/100 Mbps Ethernet card is set to operate at 100 Mbps and the hub only supports 10 Mbps, the network card will not function at all;

- network cards set to auto-negotiate rarely, if ever, auto-configure to anything but 10 Mbps and half-duplex in this environment;

- lastly, an increase in network activity is not likely because the speed at which the network card transmits has not changed -- there was no good reason why network utilization should have increased. Knowing your network and keeping tabs on network baselines should help to isolate network utilization spikes from problems when performance issues arise.
[3099]

CCIE Topic(s):
CCIE Objective(s):
CCNA Topic(s): g
CCNA Objective(s): g6

Answer
a) Switched networks offer a higher degree of security than shared media networks.
d) Switched networks provide more bandwidth per user than shared networks.

Explanation
Shared media Ethernet and Token Ring are susceptible to uninvited intrusion of network information by network neighbors because all frames are passed to all ports -- a simple connection into any network port provides access to all data that passes through the network.

Switched networks offer a higher degree of security because LAN switches forward frames only to the appropriate destination port when the destination MAC address is known to be associated with a specific port. Network neighbors are restricted to accessing frames destined for their specific workstation, broadcasts, and frames where the destination port is unknown.

Because not all frames are propagated to all ports, LAN switching offers network administrators a simple way to increase bandwidth availability to end users.

Both switched networks and shared networks have the capability to support network management. Management of the network is limited only by the capability built into the devices themselves.
[3100]

CCIE Topic(s):
CCIE Objective(s):
CCNA Topic(s): g
CCNA Objective(s): g4

[NA-LANS-SQ1-F02]
[2000-05-03-01]