Lesson 3: Deploying Ethernet Switching Flashcards
How would someone physically limit attenuation of and distance limitation of cabling?
A layer 1 repeater overcomes distance limitations of cables by boosting the signal wherever the device is placed; connects two cable segments of the same type
What is a media converter?
A layer 1 device used to transition from one cable type to a different cable type
List the typical media conversions
- Single mode fiber to twisted pair
- Multimode fiber to twisted pair
- Single mode to multimode fiber
How do hubs operate?
At the physical layer, hubs act as multiport repeaters so that every port receives transmissions sent from any other port
What limits do hubs present?
- Each hub port is part of the same collision domain
- All node interfaces are half duplex
- The bandwidth is shared between all nodes in the segment (up to 100mbps)
What interface technology is used to distinguish transmit and receive wires/pins on different interfaces?
Nodes have a medium dependent interface (MDI) while hubs have a MDI crossover (MDI-X) interface, allowing transmit wires on the host connect to the receive wires on the hub
Define an Ethernet bridge
Layer 2 device that isolates collision domains to separate segments while joining segments within the same broadcast domain allowing nodes in the separate segments to communicate
Define micro-segmentation in layer 2 switching
Each switch port is it’s own collision domain, essentially establishing a point to point link between any two network nodes
How does a collision occur in a switched network
It would only occur if the port is operating in half duplex mode due to a legacy network card or hub is attached to the switch, and even then the collision would only occur in that individual microsegment
What’s the purpose of a Network Interface Card (NIC)?
Physically connects the transceiver component to the transmission medium
How are NICs identified?
Each NIC port has a unique hardware address known as the Media Access Control (MAC) address, also known as and extended unique identifier (EUI), and local/physical address
What is the PDU in layer 2 Ethernet called?
A Frame
What makes up an Ethernet frame?
- Preamble
- SFD
- Destination and Source MAC
- Ether Type
- Payload
- FCS (Frame check sequence)
What functions do the preamble and SFD perform in an Ethernet frame?
The preamble and SFD are used for clock synchronization and as part of CSMA/CD to identify collisions early
What is the function of FCS?
Frame Check Sequence (FCS) is used to verify the integrity of the frame; the sending node calculates contents of the frame, and the receiving node does the same, if the calculations match, the receiving node accepts the frame
Define a Burned-in Address
In a MAC/EUI, this is first six hex digits that are assigned to a manufacturer by the IEE
What term defines the max size of a data payload?
Maximum Transmission Unit (MTU)
What is the max size of a data payload and what is the max size of an Ethernet frame?
- The max size of a data payload is 1500 bytes
- The max size of an Ethernet frame is 1518 bytes, excluding the preamble
What is the minimum size of an Ethernet frame
64 bytes is the minimum size of an Ethernet frame
What Ethernet standards support jumbo frames?
Gigabit and 10GbE ethernet devices support jumbo frames up to 9000 bytes
How does a software based packet sniffer operate?
Installed on a host to interrogate frames received by the network adapter by installing a driver
What are the 2 types of network packet sniffers?
- SPAN
- TAP/Powered TAP for 1GB links
What is an I/G bit?
Determines whether a frame is addressed to a single node (1) or to a group (0) for broadcast/multicast messages
Define a stackable switch topology
A group of switches connected together that operate as a single unit.
What is the difference between a modular switch and a fixed switch
Modular switches have slots for plug-in cards allowing them to have more ports and different types of ports; Fixed switches have a set number of ports.
What technology do modern switches use to detect connection type?
Auto-MDI (media dependent interface)/MDI-X
How does a switch learn MAC addresses?
By reading the source MAC address of an incoming frame and associating it with the receiving port, and finally it aches the mapping in the MAC address table
Define a MAC address table
A data store on a switch implemented as a content addressable memory (CAM) that is optimized for searching; also referred to as the CAM table
Define Flooding
If a MAC address can’t be found in the MAC/CAM table, the switch transmits the frame out of all the ports except for the source port
What is the command to query the MAC/CAM table
show mac address-table
Define port security
Specifying static MAC addresses of end systems in the configuration or allowing the port to learn and accept a certain number of MAC addresses, if the policy is not matched or a violation is detected an enforcement policy is enacted (alert or shutdown)
Define port aggregation
Combining two or more separate cable links into a single logical channel (host end defines it as NIC teaming)
How is port aggregation performed?
A pair of a NICs and cables combing to double their bandwidth capabilities
What protocol is used to implement port aggregation?
Link Aggregation Control Protocol (LACP)
Define port mirroring
Copying incoming/outgoing traffic from one or more switch ports to a specific port
What technologies use port mirroring
Used by packet sniffers, network analyzers, or IDS sensors
Define flow control and its use
An 802.3x mechanism that allows servers to instruct the switch to pause traffic temporarily to avoid overwhelming its buffer and causing it to drop frames; A switch port can be configured to pause/unpase frames
PoE switches are referred to as what type of device?
Endspan/Endpoint power sourcing equipment (PSE)
What is a power injector/midspan
A device added to non PoE switches to deliver power to endpoints
What are the types of PoE and their limits
- PoE; up to 13W
- PoE+; up to 25W
- Ultra PoE; up to 51W or 73W
Describe the function of Link Aggregation Control Protocol (LACP)
Can be used to auto-negotiate the bonded link, detect configuration errors, and recover from the failure of one of the physical links.
Describe the function of Auto-MDI/MDI-X
Determines the type of device at the other end of the cable and configures the port based on the determination to either be MDI-X uplink or crossover from switch to switch.
What is the minimum size of a data payload?
46 bytes
Describe a SPAN network sniffer
A sensor attached to a port that receives copies of frames addressed to the other ports.
Describe a TAP network sniffer
A device with ports for incoming and outgoing network cabling that copies traffic to a monitor port.
