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Understanding Ethernet and Switch Operations

Terms in this set (99)

What is carrier sense multiple access collision detect (CSMA/CD)?
CSMA/CD describes the Ethernet access method.
What is UTP cabling?
Unshielded twisted-pair (UTP) cabling is a type of twisted-pair cable that relies solely on the cancellation effects produced by the twisted wire pairs to limit electromagnetic interference (EMI) and radio frequency interference (RFI).
What is the maximum cable length for UTP?
The maximum length is 100 meters or 328 feet.
What is a straight-through Ethernet cable, and when would you use it?
A straight-through Ethernet cable is wired the same way at both ends.
What is a crossover Ethernet cable, and when would you use it?
A crossover Ethernet cable is a cable that has the send and receive wires crossed at one of the ends.
Which are the category UTP categories?
Category 1, 2, 3, 4, 5, 5e, 6, 6a.
Category 1 is Used for t[...] communications.
telephone
Category 2 is Capable of data transmission speeds of up to [...] Mbps.
4
Category 3 is Used in 1[...]-T networks, speeds up to 10 Mbps.
10BASE
Category 4 is Used in Token Ring networks, speeds up to 1[...] Mbps.
16
Category 5 is Capable of data transmission speeds of up to 1[...] Mbps.
100
Category 5e Supports speeds of up to 1 [...].
Gbps
Category 6 Consists of f[...] pairs of 24-gauge copper wires, speeds up to [...] Gbps.
four; 1
Category 6a Supports speeds up to [...] Gbps.
10
What is the difference between single-mode fiber (SMF) and multimode fiber (MMF)?
The primary difference between SMF and MMF is the ability of the fiber to send light for a long distance at high bit rates.
What are three ways that LAN traffic is transmitted?
LAN traffic is transmitted one of the following three ways: Unicast, Multicast, Broadcast.
Unicasts are the most common type of L[...] traffic.
LAN
A u[...] frame is a frame intended for only one h[...].
unicast; host
Broadcast f[...] are intended for all h[...] within a broadcast domain.
frames; hosts
Stations view broadcast frames as p[...] service announcements.
public
All s[...] receive and process broadcast frames.
stations
Multicasts are traffic in which one t[...] tries to reach only a subset, or group, of the entire s[...].
transmitter; segment
How many bits are in an Ethernet address?
Also called a MAC address, an Ethernet address is the Layer 2 address associated with the Ethernet network adapter.
Typically burned into the adapter, the MAC address is usually displayed in a h[...] format, such as 00-0d-65-ac-50-7f.
hexadecimal
What portion of the MAC address is vendor specific?
The first half or first 24 bits of the MAC address are vendor specific.
A MAC address is 4[...] bits and is displayed in h[...].
48; hexadecimal
The first half of the MAC address identifies the v[...] or m[...] of the card.
vendor; manufacturer
The first half of the MAC address is called the O[...] U[...] I[...] (OUI).
Organizational; Unique; Identifier
The last half of the MAC address identifies the c[...] address.
card
What portion of the MAC address is vendor assigned?
The last 24 bits are vendor assigned.
What are the first 24 bits in a MAC address called?
These bits are the Organizational Unique Identifier (OUI).
What is an example of a Layer 2 address?
An example is a MAC address.
What is an example of a Layer 3 address?
An example is an IP address.
If a sending device does not know the MAC address of the destination device, what protocol is used to find the MAC address of the receiving device?
Address Resolution Protocol (ARP) is used to find the MAC address of the receiving device.
ARP is a local broadcast sent to all devices on the local s[...] to find the M[...] address of a h[...].
segment; MAC; host
Host A wants to send data to host B. Host B is on a different segment from host A. The two segments are connected to each other through a router. What will host B see as the source MAC address for all frames sent from host A?
Because host B is on a different segment that is separated by a router, the MAC address of all frames sent from host A will be the MAC address of the router.
Anytime a frame passed through a router, a router r[...] the MAC address to the MAC address of the router's exit interface for the segment and then sends the frame to the local host.
rewrites
Switching uses a process outlined by the IEEE as transparent bridging. What are the five processes transparent bridges use for determining what to do with a frame?
Learning; Flooding; Filtering; Forwarding; Aging.
The five processes transparent bridges use for determining what to do with a frame are defined in IEEE 8[...].
802.1d
What is the transparent bridging learning process?
When a frame enters a switch, the switch adds the source Ethernet MAC address and source port into its MAC address table.
The process of r[...] the source MAC address and the source port in the table whenever a switch sees a frame is called the l[...] process.
recording; learning
What is the transparent bridging flooding process?
When a switch receives a unicast frame and it does not have the destination MAC address and port in its bridging table, or a broadcast or multicast frame, the switch will forward this frame out all ports, except the port it received the unicast frame on.
What is the transparent bridging filtering process?
The filtering process occurs when a switch receives a frame and the source and destination hosts reside on the same interface. When this occurs, the switch filters or discards the frame.
What is the transparent bridging forwarding process?
A switch forwards a frame when the destination address is in the switch's MAC address table and the source and destination are on different interfaces.
What is the transparent bridging aging process?
When a switch learns a source address, it time-stamps the entry in the MAC address table.
Every time the switch sees a frame from the same source, the t[...] is updated.
timestamp
The aging process occurs when the switch does not see a frame from the source before the aging timer e[...].
expires
When the aging process occurs, the switch r[...] the entry from the MAC address table.
removes
For what two purposes does the Ethernet protocol use physical addresses?
Ethernet uses physical addresses to: Uniquely identify devices at Layer 2; Allow communication between different devices on the same Layer 2 network.
Ethernet uses physical addresses to u[...] identify devices at Layer [...].
uniquely; 2
Ethernet uses physical addresses to allow c[...] between different devices on the same Layer [...] network.
communication; 2
What will an Ethernet switch do if it receives a unicast frame with a destination MAC that is listed in the switch table?
The switch will forward the frame to a specific port.
Switches use the t[...] bridging process to determine how to handle frames.
transparent
The transparent bridging process of the switches: when a frame is received, if the destination is a broadcast or multicast, the switch will f[...] the frame to all ports except to the p[...] the frame was received.
forward; port
The transparent bridging process of the switches: when a frame is received, if the destination is a unicast and the address is not in the M[...] address table, the switch forwards the frame to all p[...] except the receiving port.
MAC; ports
The transparent bridging process of the switches: when a frame is received, if the destination is a u[...], the address is in the MAC address table, and the associated interface in the MAC address table is not the r[...] interface, the switch forwards the frame to the correct interface.
unicast; receiving
Under what conditions would a switch flood a frame?
A switch will flood a frame if the MAC address table is full, if the destination MAC address has not been learned by the switch, or if the frame is a broadcast or multicast frame.
What is the switch MAC address table used for?
The switch MAC address table forwards traffic out the appropriate interface.
Because switches operate at Layer 2 of the OSI model, they switch traffic by M[...] address.
MAC
Instead of f[...] traffic out all interfaces, a switch l[...] the MAC address of devices on each interface and only forwards traffic destined to the host on the interface.
flooding; learns
The learned MAC addresses are s[...] in the switch's MAC address table.
stored
Full-duplex transmission is achieved by setting switch i[...], r[...] ports, and host N[...] to full duplex.
interfaces; router; NICs
M[...], where each network device has its own dedicated segment to the switch, ensures that full duplex will work properly.
Microsegmentation
Because the network device has its own dedicated s[...], it does not have to worry about sharing the segment with other d[...].
segment; devices
With full-duplex transmission, the device can s[...] and r[...] at the same time, effectively d[...] the amount of bandwidth between nodes.
send; receive; doubling
Three points to remember about the operation of full-duplex communication are: there are no c[...] in full-duplex mode; a dedicated s[...] p[...] is required for each full-duplex node; the h[...] network card and the switch port must be c[...] of operating in full-duplex mode.
collisions; switch; port; host; capable
What are the advantages of using full-duplex Ethernet instead of half-duplex?
Full-duplex provides faster data transfer by being able to send and receive simultaneously and operates without collisions.
By enabling full-duplex on a port, you are disabling C[...]/CD on the segment.
CSMA
How does replacing a hub with a switch affect CSMA/CD behavior in an Ethernet network?
It effectively eliminates collisions.
Replacing a hub with a switch effectively eliminates c[...] because each switch port is a s[...] collision domain.
collisions; separate
One device per switch port and configured for full-duplex operation eliminates the need for C[...]/CD.
CSMA
What command allows you to view the duplex and speed settings configured for a switch port?
show interface f0/1
Can a network hub be connected to a switch port in full-duplex mode?
No.
Because a hub s[...] access to the segment, it must connect to a switch port in half-duplex mode to be able to detect c[...].
shares; collisions
C[...]/CD is not enforced when full-duplex is c[...].
CSMA; configured
When troubleshooting a switch interface operating in full-duplex mode, which error condition can be immediately ruled out?
Collisions can be ruled out.
Remember, c[...] occur only on half-duplex l[...].
collisions; links
There are no c[...] on full-duplex links.
collisions
An end user complains of slow access to the network. You issue the show interface command on the port the end user is connected to and you see a lot of collisions and runts on the interface. What is most likely the cause of the problem?
A duplex mismatch is most likely the cause.
Although there are many things that can cause network s[...], the key here is when you issue the s[...] i[...] command, you see many collisions and runts.
slowness; show; interface
A d[...] mismatch will not only cause the end user to experience network slowness but also cause many c[...] and runts on the switch interface.
duplex; collisions
An end user complains of slow access to the network. You issue the show interface command on the port the user is connected to and you see a lot of collisions and cyclic redundancy check (CRC) errors on the interface. What can be several causes for the problem?
The most likely causes of the problem are a bad network cable, damaged media, or EMI.
Excessive collisions and CRC errors usually indicate a problem with the network c[...] attached to the port, or outside i[...].
cable; interference
You connect two switches using a straight-through UTP Cat 6 cable. The port link lights between the switches are not coming on. What is the problem?
The problem is with the cable.
A straight-through c[...] is used to connect data terminal equipment (DTE) devices to data communications equipment (DCE) devices.
cable
A switch is considered a D[...] device, and so are h[...].
DCE; hubs
DTE devices include c[...], printers, s[...], and r[...].
computers; servers; routers
For two like devices to connect to each other, a c[...] cable is needed.
crossover
If you are having connectivity issues and the port state shows "errDisable," the following issues can be causing this error: EtherChannel m[...].
misconfiguration
If you are having connectivity issues and the port state shows "errDisable," the following issues can be causing this error: D[...] mismatch.
Duplex
If you are having connectivity issues and the port state shows "errDisable," the following issues can be causing this error: B[...] protocol data unit (BPDU) port guard has been e[...] on the port.
Bridge; enabled
If you are having connectivity issues and the port state shows "errDisable," the following issues can be causing this error: U[...] Link D[...] (UDLD).
Unidirectional; Detection
If you are having connectivity issues and the port state shows "errDisable," the following issues can be causing this error: A native V[...] mismatch.
VLAN
When the switch port is receiving a lot of late collisions, the problem can be a d[...] mismatch or a f[...] port, or the d[...] between the two switches might exceed the c[...] specifications.
duplex; faulty; distance; cable
Duplex mismatches occur when the connecting ends are set to different duplex m[...], or when one end's duplex is configured and the other end is set to a[...].
modes; autonegotiation
Multiple c[...] are the number of times the transmitting port had more than one collision before successfully transmitting a f[...].
collisions; frame
If you experience multiple c[...] on a port, the problem usually lies with an o[...] medium.
collisions; oversaturated
Runts are frames smaller than 6[...] bytes with a bad frame c[...] sequence (FCS).
64; check
Bad c[...] or inconsistent duplex settings usually cause r[...].
cabling; runts
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