Additional Ethernet Features Flashcards
Features to enhance network performance, redundancy, security, management,
flexibility, and scalability
Common switch features
● Virtual LANs (VLANs)
● Trunking
● Spanning Tree Protocol (STP)
● Link aggregation
● Power over Ethernet
● Port monitoring
● User authentication
Link Aggregation (802.3ad)
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
Power Over Ethernet (PoE 802.3af, PoE+ 802.3at)
▪ 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)
Port Monitoring or Mirroring
▪ 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
User Authentication (802.1x)
▪ 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
Management Access and Authentication
▪ 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)
o Out-of-band (OOB)
Management involves keeping all network configuration devices on a
separate networ
First-Hop Redundancy
▪ 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
Other First-Hop Redundancy Protocols
▪ Gateway Load Balancing Protocol (GLBP)
● Cisco-proprietary protocol
▪ Virtual Router Redundancy Protocol (VRRP)
● Open-source protocol
▪ Common Address Redundancy Protocol (CARP)
● Open-source protocol
MAC Filtering
▪ Permits or denies traffic based on a device’s MAC address to improve
security
Traffic Filtering
▪ Multilayer switches may permit or deny traffic based on IP addresses or
application ports
Quality of Service (QoS)
Forwards traffic based on priority markings
Spanning Tree Protocol (STP) (802.1D)
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
o Broadcast Storms
▪ 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
Root and Nonroot Bridges
▪ 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
Root, Designated, and Non-Designated Ports
▪ 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
o Root and Nonroot Bridge
Single root port on non-root bridge
▪ All other ports on non-root bridge are non-designated
▪ All ports on root bridge are designated
Port States
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
Link Costs
Associated with the speed of a link
▪ Lower the link’s speed, the higher the cost
