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Which two circumstances can cause collision domain issues on VLAN domain? (Choose two.)
A. duplex mismatches on Ethernet segments in the same VLAN
B. multiple errors on switchport interfaces
C. congestion on the switch inband path
D. a failing NIC in an end device
E. an overloaded shared segment
Answer: AC
Explanation:
Collision Domains
A collision domain is an area of a single LAN where end stations contend for access to the network because all end stations are connected to a shared physical medium. If two connected devices transmit onto the media at the same time, a collision occurs. When a collision occurs, a JAM signal is sent on the network, indicating that a collision has occurred and that devices should ignore any fragmented data associated with the collision. Both sending devices back off sending their data for a random amount and then try again if the medium is free for transmission.
Therefore, collisions effectively delay transmission of data, lowering the effective throughput available to a device. The more devices that are attached to a collision domain, the greater the chances of collisions; this results in lower bandwidth and performance for each device attached to the collision domain. Bridges and switches terminate the physical signal path of a collision domain, allowing you to segment separate collision domains, breaking them up into multiple smaller pieces to provide more bandwidth per user within the new collision domains formed.
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Correct answers are A & E
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http://www.cisco.com/c/en/us/support/docs/lan-switching/virtual-lans-vlan-trunking-protocol-vlans-vtp/23637-slow-int-vlan-connect.html#troublesht_collision
If users on different collision domains (but in the same VLAN) are having the same performance issues, it still may be caused by a duplex mismatch on one or more Ethernet segments between the source and destination. The following scenario often happens: a switch is configured manually to have full-duplex on all ports in the VLAN (the default setting is “auto”), while users (network interface cards [NICs]) connected to the ports are performing an auto-negotiation procedure. This results in duplex mismatch on all ports and, therefore, bad performance on each port (collision domain). So, although it appears as if the whole VLAN (broadcast domain) is having a performance problem, it is still categorized as duplex mismatch, for the collision domain of each port.
Another case to be considered is a particular NIC performance problem. If a NIC with a performance problem is connected to a shared segment, then it may appear that a whole segment is experiencing slowness, especially if the NIC belongs to a server that also serves other segments or VLANs. Keep this case in mind because it may mislead you as you troubleshoot. Again, the best way to narrow down this issue is to perform a data transfer between two hosts on the same segment (where the NIC with the supposed problem is connected), or if only the NIC is on that port, isolation is not easy, so try a different NIC in this host, or try connecting the suspected host on a separate port, ensuring proper configuration of the port and NIC.