1B Flashcards
Some protocols and standards are _____ _____ and others proprietary to specific companies or corporations
vendor neutral
Name a few of the more common layer two applicable protocols and standards.
- PPP (Point to Point Protocol)
- STP (Spanning Tree Protocol)
- IEEE 802.1D
- Unidirectional Link Detection (UDLD) and Loopguard
- Link Layer Discovery Protocol (LLDP)
- Cisco Discovery Protocol (CDP)
- IEEE 802.1q and ISL
What does PPP stand for?
Point to Point Protocol
What does STP stand for?
Spanning Tree Protocol
What does UDLD stand for?
Unidirectional Link Detection
What does LLDP stand for?
Link Layer Discovery Protocol
What does CDP stand for?
Cisco Discovery Protocol
Which switching technology protocol does the following apply to?
- Establishes communication directly between two network devices without relying on any host or networking system.
- Operates over a point-to-point link—a link connecting two communicating link-level peers, one on each end of the link.
- It provides transmission encryption, data compression, and authentication features.
- Switches will utilize the ____ per their requirement to transfer data between nodes on a network. The ___ protocol data link layer sender must be able to take a network-level packet and frame (a.k.a encapsulate) it within the ____data link layer frame such that the receiver will be able to identify the start and end of both the data link frame, and the network layer packet within the frame.
Point to Point Protocol (PPP)
Which switching technology protocol does the following apply to?
____ _____ ______, defined by IEEE 802.1D, is a loop-prevention protocol that allows switches to communicate with each other in order to discover physical loops in a network. If a loop is found, the ____ specifies an algorithm that switches can use to create a loop-free logical topology.
The Spanning Tree Protocol (STP)
Which switching technology protocol does the following apply to?
This is the Ethernet MAC bridges standard which includes bridging, Spanning Tree Protocol and others. It is standardized by the IEEE 802.1 working group.
IEEE 802.1D
What switching technology protocol does the following apply to?
This kind of link occurs when traffic in one of two directions on a link fails. This could be caused by a bad transmitter, a bad receiver, a bad repeater, or a bad cable segment. Only one device on the link will notice a problem. This can cause a backup switch to not hear from its partner, to go into forwarding modem, and to create a switch loop because its partner is still forwarding. _____ causes the switch that is having trouble hearing to shut down the port. ______ causes the port to go into a new state: loop inconsistent state.
Unidirectional Link Detection (UDLD) and Loopguard
What switching technology protocol does the following apply to?
_____ is vendor-neutral, and is commonly used as a component for network management purposes and network monitoring applications. ____ is an open IEEE-standard layer 2 protocol. It is a vendor-neutral protocol that runs over the data link layer for heterogeneous networks and allows devices to advertise data and layer-2 configurations to their connected adjacent nodes. ____ stores MAC address, VLAN, IP management address, system names and other details, port details, MDI power, Link aggregation. One advantage of _____ is it that can run on cisco and non-cisco devices, but there is added costs for rTunning LLDP over Cisco Discovery Protocol
Link Layer Discovery Protocol (LLDP)
What switching technology protocol does the following apply to?
____ is a Cisco proprietary protocol that supports the IEEE 802.1ab version of LLDP and is primarily used to share information between directly connected Cisco devices
Cisco Discovery Protocol (CDP)
What switching technology protocol does the following apply to?
__________ is a way of encapsulating a VLAN frame that utilizes a space in the standard frame header. ISL also tags the frame but instead of using the frame as it is, ISL adds a new header and trailer to the existing frame. ISL only works with Cisco devices, where __________ works with all major manufacture’s models
IEEE 802.1q
What are the three basic and essential functions of a switch?
- Address Learning
- Forward/Filter Decision
- Loop Avoidance
The MAC address table is also known as what?
Content Addressable Memory
Address Learning Function
To function smoothly and securely, a Layer 2 switch must learn the MAC addresses of all devices that are connected to its _______.
ports
Address Learning Function Step 1
The MAC address table (also known as Content Addressable
Memory) is stored in the switches RAM. When the switch is first put into service, the table is ________.
empty
Address Learning Function Step 2
When any attached device transmits a frame, the switch takes the _____ ______ and places it in the MAC address table along with the interface ID on which the device is connected.
source address
Address Learning Function Step 3
Because the destination hardware address is not listed in the switch’s MAC address table, the frame is _________ out all active interfaces (ports) except the interface from which the frame was received.
flooded (broadcast)
Address Learning Function Step 4
When the device answers the flood, the switch adds that devices information (MAC address, and interface ID) to the MAC address table. The switch now has the two MAC addresses in its table. If those two computers now send frames to each other, the switch will make a _____-__-_____ connection and frames destined for those computers will only be forwarded between the two devices. The switch has learned those MAC addresses attached to those interfaces and does not need to flood all interfaces. This process continues until the switch knows all connected devices.
point-to-point
The Layer 2 switch also uses the MAC address table to both forward and filter frames received on the switch. This is called…?
Forward/Filter Decision
Described below is the process for the Forward/Filter Decision - How does the below information help the Address Learning Function?
When a frame arrives at a switch interface, the destination hardware address is compared to the forward/filter MAC database. If the
destination hardware address is listed in the MAC address table, the frame is only forwarded out the interface identified with the host. The frame is not sent out any other interface. This process is the frame filtering.
This helps to fully utilize bandwidth on all network segments attached to the switch.
The final switch function is _____ ______.
loop avoidance
Why are loops required?
Switches in a network environment can create a “single point of failure” in the network topology. To overcome a single point of failure, it
is a good idea to use multiple links (paths) between switches or use multiple switches. As a result of the multiple links or use of multiple switches, loops are created which can have a crippling effect on network wide operation by endlessly repeating the retransmission of a frame.
Loops can cause instability in the switch’s MAC address table. This instability can present itself as what three problems?
- Broadcast storms
- Multiple frame copies
- Multiple loops
Broadcast storms are also known as what?
Network storm
The following describes what problem resulting from looping?
Occurs when a network system is overwhelmed by the continuous multicast of broadcast traffic. When different nodes are sending broadcast data over a network link, and the other network devices are rebroadcasting the data back to the network link in response, this process eventually overwhelms the whole network and leads to the failure of network communication.
Broadcast Storms
What are some examples of reasons that cause Broadcast Storms?
Poor technology, low port rate switches and improper network configurations.
The following describes what problem that results from looping?
Another problem is a device can receive multiple copies of the same frame of information because the frame can arrive from different LAN segments at the same time.
Multiple Frame Copies
The following describes what?
Multiple frames can arrive from multiple segments simultaneously. The result of this is the MAC address filter table becomes confused as to where a device (Server/host X) is located because the switch can receive the frame from more than one link. It is possible that the switch can’t forward a frame because it is constantly updating the MAC filter table with source hardware address locations.
This is called thrashing the MAC table
The following describes what problem that results from looping?
This means that loops can occur within other loops. If a broadcast storm were to occur, any usable bandwidth would be consumed by the storm and result in the network not able to perform packet switching.
Multiple loops
Loops (redundant links) are _________ in a network.
necessary
What protocol created a standardized solution for Loop Avoidance?
Switches can be configured to avoid loops. _____ standardized a solution to prevent bridging loops in data networks and provide
loop-free topologies.
IEEE 802.1D
The standardized solution for Loop Avoidance is called _____ _____ ______.
Spanning Tree Protocol (STP)
What are the three switching methods?
Store-and-forward, Cut-Through, and Fragment Free
The following describes what switching method?
____-_____ switches store the entire frame in internal memory and check the frame for errors before forwarding the frame to its destination. The error check is done through a cyclical redundancy
check (CRC), which is a mathematical calculation based on the number of (1s) in the frame. If an error is found, the frame is discarded, and an error message is sent to the sender MAC address for that frame. ___-___ ensures a high level of error-free traffic because bad frames are discarded instead of being sent across the network.
Store-and-forward switching
The following describes what switching method?
___-______ switching copies only the destination MAC address into memory. The switch looks up the address in its switching table and places the frame on the outgoing interface. ___-____ switching reduces latency; however, bad frames are forwarded, and the destination will ultimately have to request the source send the frame again.
Cut-through switching
The following describes what switching method?
____-____ Switching is a hybrid of Store-and-Forward and Cut-Through switching. ___-____ stores the first 64 bytes before forwarding. If there is fragmentation, the frame is discarded, and an error message is sent to the sender MAC address for that frame. The reason ___-___ only checks the first 64 bytes is because that is where frame fragmentation is most likely to happen.
Fragment-free switching
When two system transmissions occur at the same time, on shared bandwidth, the result is a collision. Collisions are a part of Ethernet communications and do not imply any _____ ______.
error condition
