Switching Concepts
Which impact does adding a Layer 2 switch have on a network?
a. an increase in the number of dropped frames
b. an increase in the size of the broadcast domain
c. an increase in the number of network collisions
what is
b. an increase in the size of the broadcast domain
Adding a Layer 2 switch to a network increases the number of collision domains and increases the size of the broadcast domain. Layer 2 switches do not decrease the amount of broadcast traffic, do not increase the amount of network collisions and do not increase the number of dropped frames.
This item references content from the following areas:
Switching, Routing, and Wireless Essentials
2.2 Switching Domains
How do switch buffers affect network performance?
a. They provide error checking on the data received.
b. They store frames received, thus preventing premature frame discarding when network congestion occurs.
c. They provide extra memory for a particular port if autonegotiation of speed or duplex fails.
what is
b. They store frames received, thus preventing premature frame discarding when network congestion occurs.
Switches have large frame buffers that allow data waiting to be transmitted to be stored so the data will not be dropped. This feature is beneficial especially if the incoming traffic is from a faster port than the egress port used for transmitting.
This item references content from the following areas:
Switching, Routing, and Wireless Essentials
2.2 Switching Domains
Which characteristic describes cut-through switching?
a. Error-free fragments are forwarded, so switching occurs with lower latency.
b. Frames are forwarded without any error checking.
c. Only outgoing frames are checked for errors.
what is
b. Frames are forwarded without any error checking.
Cut-through switching reduces latency by forwarding frames as soon as the destination MAC address and the corresponding switch port are read from the MAC address table. This switching method does not perform any error checking and does not use buffers to support different Ethernet speeds. Error checking and buffers are characteristics of store-and-forward switching.
This item references content from the following areas:
Switching, Routing, and Wireless Essentials
2.1 Frame Forwarding
Which switch characteristic helps keep traffic local and alleviates network congestion?
a. high port density
b. fast port speed
c. large frame buffers
what is
a. high port density
Switches that have a lot of ports (high port density) reduce the number of switches required and keep some of the traffic locally on the switch, thus removing the need to send it between switches.
This item references content from the following areas:
Switching, Routing, and Wireless Essentials
2.2 Switching Domains
What is the significant difference between a hub and a Layer 2 LAN switch?
a. A hub extends a collision domain, and a switch divides collision domains.
b. A hub divides collision domains, and a switch divides broadcast domains.
c. Each port of a hub is a collision domain, and each port of a switch is a broadcast domain.
what is
a. A hub extends a collision domain, and a switch divides collision domains.
Hubs operate only at the physical layer, forwarding bits as wire signals out all ports, and extend the collision domain of a network. Switches forward frames at the data link layer and each switch port is a separate collision domain which creates more, but smaller, collision domains. Switches do not manage broadcast domains because broadcast frames are always forwarded out all active ports.
This item references content from the following areas:
Switching, Routing, and Wireless Essentials
2.2 Switching Domains
Which switch component reduces the amount of packet handling time inside the switch?
a. ASIC
b. dual processors
c. large buffer size
what is
a. ASIC
Application-specific integrated circuits (ASICs) are used in Cisco switches to speed up switch operations so that the switch can have an increased number of ports without degrading switch performance.
This item references content from the following areas:
Switching, Routing, and Wireless Essentials
2.1 Frame Forwarding
Which statement is correct about Ethernet switch frame forwarding decisions?
a. Frame forwarding decisions are based on MAC address and port mappings in the CAM table.
b. Cut-through frame forwarding ensures that invalid frames are always dropped.
c. Only frames with a broadcast destination address are forwarded out all active switch ports.
what is
a. Frame forwarding decisions are based on MAC address and port mappings in the CAM table.
Cut-through frame forwarding reads up to only the first 22 bytes of a frame, which excludes the frame check sequence and thus invalid frames may be forwarded. In addition to broadcast frames, frames with a destination MAC address that is not in the CAM are also flooded out all active ports. Unicast frames are not always forwarded. Received frames with a destination MAC address that is associated with the switch port on which it is received are not forwarded because the destination exists on the network segment connected to that port.
This item references content from the following areas:
Switching, Routing, and Wireless Essentials
2.1 Frame Forwarding
What information is added to the switch table from incoming frames?
a. source MAC address and incoming port number
b. destination MAC address and incoming port number
c. source IP address and incoming port number
what is
a. source MAC address and incoming port number
A switch "learns" or builds the MAC address table based on the source MAC address as a frame comes into the switch. A switch forwards the frame onward based on the destination MAC address.
This item references content from the following areas:
Switching, Routing, and Wireless Essentials
2.1 Frame Forwarding