Chapter 10: Analyzing Ethernet LAN Designs Flashcards
Which of the following devices would be in the same collision domain as PC1?
a. PC2, which is separated from PC1 by an Ethernet hub
b. PC3, which is separated from PC1 by a transparent bridge
c. PC4, which is separated from PC1 by an Ethernet switch
d. PC5, which is separated from PC1 by a router
a. PC2, which is separated from PC1 by an Ethernet hub
Which of the following devices would be in the same broadcast domain as PC1?
(Choose three answers.)
a. PC2, which is separated from PC1 by an Ethernet hub
b. PC3, which is separated from PC1 by a transparent bridge
c. PC4, which is separated from PC1 by an Ethernet switch
d. PC5, which is separated from PC1 by a router
A,B,C
In a two-tier campus LAN design, which of the following are typically true of the topology design? (Choose two answers.)
a. The design uses a full mesh of links between access and distribution switches
b. The design uses a partial mesh of links between access and distribution switches
c. The design uses a partial mesh of links between the distribution and core switches
d. The end user and server devices connect directly to access layer switches
B,D
In a three-tier campus LAN design, which of the following are typically true of the topology design? (Choose two answers.)
a. The design uses a partial mesh of links between access and distribution switches
b. The design uses a full mesh of links between access and distribution switches
c. The design uses a partial mesh of links between the distribution and core switches
d. The end user and server devices connect directly to distribution layer switches
A,C
Which one answer gives the strongest match between one part of a typical three-tier design with the idea behind the listed generic topology design term?
a. The access layer looks like a partial mesh.
b. The distribution layer looks like a full mesh.
c. The distribution layer looks like a hybrid design.
d. The access layer looks like a star design.
D
Which of the following Ethernet standards support a maximum cable length of longer than 100 meters? (Choose two answers.)
a. 100BASE-T
b. 1000BASE-SX c. 1000BASE-T d. 1000BASE-LX
B,D
A collision domain
the set of NICs and device ports for which if they sent a frame at the same time, the frames would collide.
ummarizing the key points about hubs:
■ The hub acts a multiport repeater, blindly regenerating and repeating any incoming elec- trical signal out all other ports, even ignoring CSMA/CD rules.
■ When two or more devices send at the same time, the hub’s actions cause an electrical collision, making both signals corrupt.
■ The connected devices must take turns by using carrier sense multiple access with colli- sion detection (CSMA/CD) logic, so the devices share the bandwidth.
■ Hubs create a physical star topology.
How do bridges forward frames?
bridges hold Ethernet frames in memory, waiting to send out the outgoing interface based on CSMA/CD rules
key points about collision domains:
■ LAN switches place each separate interface into a separate collision domain.
■ LAN bridges, which use the same logic as switches, placed each interface into a separate collision domain.
■ Routers place each LAN interface into a separate collision domain. (The term collision domain does not apply to WAN interfaces.)
■ LAN hubs do not place each interface into a separate collision domain.
■ A modern LAN, with all LAN switches and routers, with full duplex on each link, would not have collisions at all.
■ In a modern LAN with all switches and routers, even though full duplex removes colli- sions, think of each Ethernet link as a separate collision domain when the need to trou- bleshoot arises.
Def: Broadcast domain
where a broadcast sent by any one device would be flooded to all devices connected to all switches (except for the device that sent the original frame).
Summarizing the main points about broadcast domains:
■ Broadcasts exists, so be ready to analyze a design to define each broadcast domain, that is, each set of devices whose broadcasts reach the other devices in that domain.
■ VLANs by definition are broadcast domains created though configuration.
■ Routers, because they do not forward LAN broadcasts, create separate broadcast
domains off their separate Ethernet interfaces.
Access switches
onnect directly to end users, providing user device access to the LAN. Access switches normally send traffic to and from the end-user devices to which they are connected and sit at the edge of the LAN.
Distribution switches
provide a path through which the access switches can forward traffic to each other. By design, each of the access switches connects to at least one distribution switch, typically to two distribution switches for redundancy. The distribution switches provide the service of forwarding traffic to other parts of the LAN. Note that most designs use at least two uplinks to two different distribution switches (as shown in Figure 10-10) for redundancy.
formal definitions of four topology terms:
Star: A design in which one central device connects to several others, so that if you drew the links out in all directions, the design would look like a star with light shining in all directions.
Full mesh: For any set of network nodes, a design that connects a link between each pair of nodes.
Partial mesh: For any set of network nodes, a design that connects a link between some pairs of nodes, but not all. In other words, a mesh that is not a full mesh.
Hybrid: A design that combines topology design concepts into a larger (typically more complex) design.
