Ethernet Switching Features

Question 1

Unmanaged Switch

Answer 1

• Standalone unit that can be added and run without configuration
• Often built into router and modem on SOHOs

Question 2

Managed Switch

Answer 2

• Switch settings can be configured

- If left unconfigured, acts as unmanaged switch

Question 3

Stackable Switch

Answer 3

• Can be connected and managed as one unit

Question 4

Modular vs Fixed Switch

Answer 4

• Modular switch has slots for plugins which can change number and types of ports

Question 5

Desktop vs rack-mounted Switch

Answer 5

• Smaller unmanaged switch weith 5-8 ports may be placed on desktops
• Larger switches are fitted to work in rack space

Question 6

MDI/MDI-X

Answer 6

• In 100BASE-T end system uses MDI to transmit on pins 1-2 and receive on 3-6 (uplink port)
• Switches use MDI-X Xand receives on 1-2 and transmits on 3-6
• Cable should be a Straight through (either T568A or B on both ends)
• Communication between switches would require crossover cable or dedicated uplink port(which has A on one end and B on the other)
• Most switches use auto-MDI/MDIX now which fixes this problem.

Question 7

MAC Address Table

Answer 7

• Switch learns MAC addresses by reading source MACs on port it receives it on
• If MAC cannot be found then switch acts as hub and transmits frame on all ports (flooding)
• Also referred to as CAM (content addressable memory) table
• Entries on table are flushed after a period of time

Question 8

Port Security

Answer 8

• Validates MAC address of end systesm that connect to switch port
• Usually you would not expenct MACs’ of devices to change often
• Two components:
• Specify a static MAC or allow port to accept certain number of addresses
• Specify an enforcement function which violation is detected (alert or shutdown port)

Question 9

Port Aggregation

Answer 9

• Combining two or more cabled links into single logical channel
• From host end can be call NIC Teaming
• Oftetn implemented with LACP (Link Aggregation Control Protocol)
• LACP is used to autonegotiate bonded link between swithc ports and end system

Question 10

Port Miroring

Answer 10

• Copies all packets sent to one or more source ports to a mirror destination port
• Used by packet sniffer, network analyzer of IDS(intrusion detection system).
• Ingress or egress traffic can be captured.
• Can be filtered based on protocl ID or TCP/UDP port number

Question 11

Jumbo Frames

Answer 11

• Allow for larger frames (up to 9000 bytes)
• Reduces amout of processing necessary by switches and routers
• Benefits are disputed
• Critical that all hosts and appliances on communications path are configured to suport them

Question 12

Flow Control

Answer 12

• Allows server to instruct switch to pause traffic temporarily
• Used to avoid overwhelming buffer and causing dropped frames
• IEEE 802.3x cannot distinguish between types of traffic
• CoS and QoS (Class and quality of Service) mechanisms can be allied to mark and police traffic
• PFC(priority flow control 802.1 Qbb) allows pause frames to apply to only certain traffic

Question 13

Show config

Answer 13

• CLI command for managed switch
• displays switches configuration
• can be used to compare changes to documentation

Question 14

Show interface

Answer 14

• CLI command for managed switch
• lists state of all interfaces or specified interface
• Identified by type, slot and port number

Question 15

802.3af

Answer 15

Power over Ethernet

-Up to 13 W over link

Question 16

802.3at

Answer 16

PoE+

- up to 25W