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Layer 2 and Layer 3 Switching
Freeha Khan
2nd PresentationIS 8040
Data Communication Theory and Practice
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Switching
Today in data communications, all switchingand routing equipment perform two basicoperations:
Switching data frames Maintenance of switching operations
Switching is the process of taking anincoming frame from one interface and
delivering it out through another interfaceRouters use Layer 3 switching to route apacket, and switches (Layer 2 switches) useLayer 2 switching to forward frames
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Switches
Switches are similar to bridges but usuallyhave more ports
Switches provide a unique network segmenton each port, thereby separating collisiondomains
Today, network designers are replacing hubs
in their wiring closets with switches toincrease their network performance andbandwidth while protecting their existingwiring investments
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Switches
10/100-Mbps Ethernet Switches are goodresolution if Ethernet LANs are stretched to
the breaking point under the weight of new users, servers and high-end applications
Most switches provide shared or dedicated10/100 uplinks to other switches or network
backbones, and some even provide one ortwo dedicated Gigabit Ethernet links forespecially heavy bandwidth requirements
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Layer 2 Switching
Layer 2 switches,operate at the
second, or data link,layer of the opensystemsinterconnection
model
OSI Model
Application
Presentation
Session
Transport
Network
Data Link
Physical
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Layer 2 Switch
Garrett Communications Magnum switchescome with eight to 24 10/100-Mbps ports andrange in price from $599 to $1,199.
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Layer 2 Switching
Layer 2 switches operate at MAC layer
Layer 2 switches broadcast multicast traffic to all
their ports
very detrimental to performance
Static entries can be defined on switches to
control multicast at layer 2 but static entries do
not react to dynamic behaviors
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Layer 2 Switching
Check incoming network traffic
Keep track of the physical addresses of all
stations attached to their portsForward traffic to specific station addressesaccording to the forwarding tables
Layer 2 switches can deliver data at wirespeeds because they dont have to examineindividual data packets
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Layer 2 Switching
Flow of intersubnet traffic with Layer 2 switches and
routers
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Layer 2 Switching
If the Layer 2 switch does not know where to
send the frame, it broadcasts the frame out all its
ports to the network to learn the correctdestination
When the frame's reply is returned, the switch
learns the location of the new address and addsthe information to the switching table
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Layer 3 Switching
Layer 3 switchingoperates at the
network layer
OSI Model
Application
Presentation
Session
Transport
NetworkData Link
Physical
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Layer 3 Switch
Limited-purpose
Layer 3 switches are only available forEthernet
They only route IP/IPX protocols
Capable to perform routing at wirespeed: 10, 100, 1000 Mbps
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Layer 3 Switching
Hardware based packet-to-packet IP
routing
Hardware based routers cost less than
traditional software-based routers
They switch non-routable traffic to Layer 2
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Layer 3 Switch
RapierTM 10/100 Layer 3 Switch
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Layer 3 Switching
It examinespacketinformation andforwards packets based on their
network-layer destination addresses
Layer 3 switching also supportsrouter functionality
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Layer 3 Switching
Flow of intersubnet traffic with Layer 3 switches
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Difference between Layer 2 and
Layer 3 SwitchesThe difference between Layer 2 and Layer 3switching is the type of information inside the
frame that is used to determine the correctoutput interface
With Layer 2 switching, frames are switchedbased on MAC address information
With Layer 3 switching, frames are switchedbased on network-layer information
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Difference between Layer 2 and
Layer 3 SwitchesLayer 2 switching does not lookinside a packet for network-layer
information as does layer 3switching
Layer 2 switching is performed by
looking at a destination MACaddress within a frame
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Difference between Layer 2 and
Layer 3 SwitchesLayer 3 switches looks at the frame'sdestination address and sends it to the
appropriate interface if it knows thedestination address location
Layer 2 switching builds and maintains
a switching table that keeps track ofwhich MAC addresses belong to eachport or interface
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References
Switched, Fast, and Gigabit Ethernet, Robert
Breyer and Sean Riley, Third Edition
Business Data Communications, Stallings,Fourth Edition
http://www.gcn.com
http://www.slac.stanford.edu/
http://www.cisco.com/univercd
http://www.gcn.com/http://www.slac.stanford.edu/http://www.cisco.com/univercdhttp://www.cisco.com/univercdhttp://www.slac.stanford.edu/http://www.gcn.com/7/30/2019 Switching (Layer 2 and Layer 3 Switching)
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References
http://www.gcn.com/state/vol6_no9/guide/837-
2.html
http://www.msic.com
http://www.gcn.com/state/vol6_no9/guide/837-2.htmlhttp://www.gcn.com/state/vol6_no9/guide/837-2.htmlhttp://www.msic.com/http://www.msic.com/http://www.gcn.com/state/vol6_no9/guide/837-2.htmlhttp://www.gcn.com/state/vol6_no9/guide/837-2.htmlhttp://www.gcn.com/state/vol6_no9/guide/837-2.html