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CISCO NETWORKING ACADEMY CISCO NETWORKING ACADEMY Chabot College Chabot College ELEC 99.05 ELEC 99.05 Ethernet Switches
| Date post: | 17-Jan-2018 |
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CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Chabot CollegeChabot College
ELEC 99.05ELEC 99.05Ethernet Switches
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Ethernet Switch BasicsEthernet Switch Basics• Layer 2 device• Uses MAC addressing to control traffic flow• Supports multiple simultaneous
conversations• Reduces needless LAN traffic
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Basics: Layer 2 DeviceBasics: Layer 2 Device• Switch understands layer 2 addresses
(MAC addresses):
00-C0-F0-56-BD-98
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Basics: MAC Address UseBasics: MAC Address Use• Switch does not act like hub!• Switch forwards frames based on
MAC address tables.
I
H
G
FEDA B C
MAC AddressTable
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Basics: MAC Address UseBasics: MAC Address Use• Switch “learns” MAC addresses of hosts
connected to switch ports as it receives frames from those ports:
I
H
G
FEDA B C
AC E
G H
MAC AddressTable
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Basics: Multiple Data PathsBasics: Multiple Data Paths• Switch can create several simultaneous data
paths or “conversations”:
B C D E F G I
A
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Switches Reduce Needless Switches Reduce Needless LAN TrafficLAN Traffic
• Each switch port defines a collision domain.
• Users on hub Aonly see trafficfrom/to theirworkgroup.
Hub Hub
Switch - 1 port per hub
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Advanced FeaturesAdvanced Features• Switching matrix• Addressing• Multiple data rates• Full duplex• Port trunking• VLANs• Inter-switch communications• Modular Chassis
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Switching Matrix (Fabric)Switching Matrix (Fabric)• Store & Forward
– stores entire incoming frame in memory buffer– performs error detection– drops bad frames– forwards good frames to destination port
based on MAC address– takes time - “high latency”
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Switching Matrix (Fabric)Switching Matrix (Fabric)• Cut-through (cross-point)
– reads frame only as far as destination address field
– immediately forwards all frames to destination port based on MAC address
– no error checking; forwards bad frames(usually not a serious problem)
– fast - “low latency” (“wire speed”)
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Addressing CapabilityAddressing Capability• 1 MAC address per port
– used with “port switching”
– microsegmentation
Switch - 1 port per PC
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Addressing CapabilityAddressing Capability• 1 MAC address per port
– used with “port switching”– microsegmentation
• Multiple MAC addresses per port– used with “segment
switching”
Switch - 1 port per PC
Hub Hub
Switch - 1 port per hub
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Multiple Data Transfer RatesMultiple Data Transfer Rates• Ports at 10mb/s and 100 mb/s• Requires “flow control”
B C D E F G I
Server
100
10 10 10 10 10 10 10
Otherwise, a fast server on a 100 mb portcould overflow the buffer of a 10 mb port.
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Full Duplex PortsFull Duplex Ports• Ports can transmit & receive simultaneously.• Useful mainly for servers.• Possible only when there is one host per port
(no collisions).• Modern NICs “auto-sense” a full-duplex
switch port& turn on FD.
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Port TrunkingPort Trunking• Ports can “trunked” (linked together) to form a
high bandwidth channel between switches:
300
CampusCore
Switch
BuildingSwitch
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Tiered BandwidthTiered Bandwidth• Bandwidth can be placed where it is needed
most:
Workgroup Switch
D E F G I
100
10 10 10 10 10
Workgroup Switch
J K L M N
100
10 10 10 10 10
300
CampusCore
Switch
BuildingSwitch
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
VLANsVLANs• Switch ports can be separated into groups
called VLANs (virtual LANs)
VLAN1 VLAN2
D E F G I J
LAN2
D E F G I J
LAN1 sameas
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
VLANsVLANs• Each VLAN forms a broadcast domain.• Each VLAN is a separate Local Area Network
VLAN1 VLAN2
D E F G I J
LAN2
D E F G I J
LAN1 sameas
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
VLANsVLANs• VLAN can be cross-connected by routers.
(just like LANs)
VLAN1 VLAN2
D E F G I J
LAN2
D E F G I J
LAN1 sameas
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Inter-Switch CommunicationInter-Switch Communication• Vendor-specific frame technologies allow
switches to communicate.• Cisco’s version is ISL (Inter Switch Link)• Allows VLANs to span several switches.• Hosts G, I, J, K are all part of VLAN 2:
D E F G I J K L M N
VLAN1 VLAN2 VLAN2 VLAN3
ISL
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Modular ChassisModular Chassis• Large switches often use a modular chassis
that accepts various:– “switching engines”– interface modules– power supplies
• The Cisco Catalyst 5000 and 5505 are examples used on the Chabot campus
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Catalyst 5000 ChassisCatalyst 5000 ChassisSD
POWER115/230 VAC9.8/4.9 A60/50Hz
POWER115/230 VAC9.8/4.9 A60/50Hz
1
1
1
1
1STATUS
SUPERVISOR ENGINE
FAN
PS2
PS1 RESET 100%SWITCH
LOAD1%
100Mbps
LINK
MDI X
100Mbps
LINK
MDI X
STATUS
ETHERNET SWITCHING MODULE
TXRX TX
RX TXRX TX
RX TXRX TX
RX TXRX TX
RX TXRX TX
RX TXRX TX
RX
1 2 3 4 5 6 7 8 9 10 11 12
ETHERNET SWITCHING
STATUS 1-4 5-8 9-1213-16
17-2021-24
ETHERNET SWITCHING
STATUS 1-4 5-8 9-1213-16
17-2021-24
STATUS
ETHERNET SWITCHING MODULE
TXRX TX
RX TXRX TX
RX TXRX TX
RX TXRX TX
RX TXRX TX
RX TXRX TX
RX
1 2 3 4 5 6 7 8 9 10 11 12
