Additional Ethernet Features

Question 1

Features to enhance network performance, redundancy, security, management,
flexibility, and scalability

Answer 1

Common switch features
● Virtual LANs (VLANs)
● Trunking
● Spanning Tree Protocol (STP)
● Link aggregation
● Power over Ethernet
● Port monitoring
● User authentication

Question 2

Link Aggregation (802.3ad)

Answer 2

Congestion can occur when ports all operate at the same speed
▪ Allows for combination of multiple physical connections into a single
logical connection
▪ Bandwidth available is increased and the congestion is minimized or
prevented

Question 3

Power Over Ethernet (PoE 802.3af, PoE+ 802.3at)

Answer 3

▪ Supplies electrical power over Ethernet
● Requires CAT 5 or higher copper cable
● Provides up to 15.4 watts of power to device
● PoE+ provides up to 25.5 W of power to device
▪ Two device types
● Power Sourcing Equipment (PSE)
● Powered Device (PD)

Question 4

Port Monitoring or Mirroring

Answer 4

▪ Helpful to analyze packet flow over network
● Connect a network sniffer to a hub and it sees all
● But, switches require port monitoring for network analyzer to see
all the traffic
▪ Port mirroring makes a copy of all traffic destined for a port and sends it
to another port

Question 5

User Authentication (802.1x)

Answer 5

▪ For security purposes, switches can require users to authenticate
themselves before gaining access to the network
▪ Once authenticated, a key is generated and shared between the
supplicant (device wanting access) and the switch (authenticator)
Authentication server checks the supplicant’s credentials and creates the
key
▪ Key is used to encrypt the traffic coming from and being sent to the client

Question 6

Management Access and Authentication

Answer 6

▪ To configure and manage switches, you can use two options:
● SSH
o Remote administration program that allows you to
connect to the switch over the network
● Console port
o Allows for local administration of the switch using a
separate laptop and a rollover cable (DB-9 to RJ-45)

Question 7

o Out-of-band (OOB)

Answer 7

Management involves keeping all network configuration devices on a
separate networ

Question 8

First-Hop Redundancy

Answer 8

▪ Hot Standby Router Protocol (HSRP) uses virtual IP and MAC addresses to
provide a “active router” and a “standby router”
● HSRP is a Cisco-proprietary protocol
● If Active is offline, then standby answers

Question 9

Other First-Hop Redundancy Protocols

Answer 9

▪ Gateway Load Balancing Protocol (GLBP)
● Cisco-proprietary protocol
▪ Virtual Router Redundancy Protocol (VRRP)
● Open-source protocol
▪ Common Address Redundancy Protocol (CARP)
● Open-source protocol

Question 10

MAC Filtering

Answer 10

▪ Permits or denies traffic based on a device’s MAC address to improve
security

Question 11

Traffic Filtering

Answer 11

▪ Multilayer switches may permit or deny traffic based on IP addresses or
application ports

Question 12

Quality of Service (QoS)

Answer 12

Forwards traffic based on priority markings

Question 13

Spanning Tree Protocol (STP) (802.1D)

Answer 13

o Permits redundant links between switches and prevents traffic loops
o Availability is measured in 9’s
▪ Five 9’s is 99.999% uptime and allows only 5 minutes down per year
o Shortest Path Bridging (SPB) is used for larger network environments instead

Question 14

o Broadcast Storms

Answer 14

▪ If broadcast frame received by both switches, they can forward frames to
each other
▪ Multiple copies of frame are forwarded, replicated, and forwarded again
until the network is consumed with forwarding many copies of the same
initial frame

Question 15

Root and Nonroot Bridges

Answer 15

▪ Root bridge
● Switch elected to act as a reference point for a spanning tree
● Switch with the lowest bridge ID (BID) is elected as the root bridge
● BID is made up of a priority value and a MAC address (with the
lowest value considered root)
▪ Nonroot bridge
● All other switches in an STP topology
▪ MAC Address table corruption can occur

Question 16

Root, Designated, and Non-Designated Ports

Answer 16

▪ Root Port
● Every non-root bridge has a single root port
● Port closest to the root bridge in terms of cost
● If costs are equal, lowest port number is chosen
▪ Designated Port
● Every network segment has a designated port
● Port closest to the root bridge in terms of cost
● All ports on root bridge are designated ports
▪ Non-Designated Port
● Ports that block traffic to create loop-free topology

Question 17

o Root and Nonroot Bridge

Answer 17

Single root port on non-root bridge
▪ All other ports on non-root bridge are non-designated
▪ All ports on root bridge are designated

Question 18

Port States

Answer 18

Non-designated ports do not forward traffic during normal operation, but
do receive bridge protocol data units (BPDUs)
▪ If a link in the topology goes down, the
non-designated port detects the failure and determines whether it needs
to transition to a forwarding state
▪ To get to the forwarding state, though, it has to transition through four
states
▪ Blocking
● BPDUs are received but they are not forwarded
● Used at beginning and on redundant links
▪ Listening
● Populates MAC address table
● Does not forward frames
▪ Learning
● Processes BPDUs
● Switch determines its role in the spanning tree
▪ Forwarding
● Forwards frames for operations
▪ Root and Non-designated port are blocking
▪ Designated ports are forwarding

Question 19

Link Costs

Answer 19

Associated with the speed of a link
▪ Lower the link’s speed, the higher the cost