Chapter 11 - Supplement - Sheet1 Flashcards
Benefits of layer 2 switching
Hardware-based bridging (ASIC), Wire speed, low latency, low cost
ASIC
Application-specific integrated circuits. Switches make decisions based on ASIC chips (hardware) instead of software, like how bridges operate
Limitations of Layer 2 Switching
Switches don’t break up broadcast domains, only collision domains
Three functions of layer 2 switching
Address learning, forward/filter decisions, loop avoidance
Address Learning
Switches build a forward/filter table of MAC addresses from the source field of packets sent to them.
Two version of the IEEE Spanning Tree Protocol
802.1D, 802.1w
5 problems that can affect data as it traverses network cable
Delay, Dropped Packets, Error, Jitter, Out-of-order delivery
Access Ports
Belongs to and carries the traffic of only one VLAN
Trunk Ports
Carries multiple VLANs at a time
Trunk Link
100Mbps or 1000Mbps point-to-point link between two switches, between a switch and a router, or between a switch and a server.
Max VLANS trunk links can carry traffic for
4094
Two VLAN identification methods
ISL, 802.1q
ISL
VLAN ID method. Inter-Switch Link - Encapsulates the data frame with its own header (that has a VLAN ID) and a CRC. Proprietary to Cisco. Fast Ethernet and Gigabit Ethernet only
IEEE 802.1Q
VLAN ID method. Inserts a field into the frame to ID the VLAN.
VTP
VLAN Trunking Protocol. Allows for management of VLANs throughout the network via a server or central switch
Default VTP mode for switches
VTP Server
VTP modes
Server, client, transparent
PoE
Power over ethernet
PoE IEE standard
802.3.af
PoE Plus
POE with more power
PoE Plus IEEE standard
802.3at
Port Mirroring
AKA SPAN (Switch Port Analyzer). Allows you to simulate a port on a switch from another point on the switch, which anables traffic sniffing of data going out a specific port
STP
Spanning tree protocol.
Main purpose of STP
Prevent switching lops in a network with redundant switched ports
States of STP
Blocking, Listening, Learning, Forwarding, Disabled
Blocking State STP
Preent the use of looped paths
Listening State STP
Prepared to forward data frames without populating the MAC address table
Learning State STP
Populates the MAC address table but doesn’t forward data frames
Forwarding State STP
Sends and received all data frames on a bridged port
Disabled State STP
Virtually nonooperational.
VLANs break up ________ domains in a Layer 2 switched network.
Broadcast
Switches, by default, only break up ________ domains.
Collission
What does trunking provide?
Allows you to send information about many or all VLANs through the same link.
You need to power a device such as an access point or IP phone. What protocol can provide power to these devices over an Ethernet cable?
PoE
You plug a host into a switch port and the host receives an IP address but the user can’t get to the services it needs. What is probably the problem?
VLAN port membership could be wrong
If a destination MAC address is not in the forward/filter table, what will the switch do with the frame?
Flood the frame out all ports except the port on which it was received
What are the three switch functions at Layer 2?
Address learning, filtering, and loop avoidance
If a frame is received on a switch port and the source MAC address is not in the forward/filter table, what will the switch do?
It will add the source MAC address to the forward/filter table
What is used at Layer 2 to prevent switching loops?
Spanning tree protocol.
You need to implement a separate network for contractors and guests working at your office. Which technology should you implement?
Create a VLAN for contractors and another for guests
