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CSIS 4823Data Communications
Networking – Designing Networks
Mr. Mark Welton
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Three-tiered Architecture Collapsed core – no distribution Collapsed core – no distribution or access
Network Designs
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Most common design when network covers multiple buildings
Physical separation of the three levels usually occurs when there is a physical need to do so
Access devices are connected at the access-layer switches
These switches connect to the distribution-layer switches
Distribution-layer switches then connect to the core-layer
Internet and server farm (data center) typically connect to the core-layer
Three-tiered Architecture
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Three-tiered Architecture
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Common in single building designs with multiple floors
Distribution-layer switches are removed and access layer goes directly in core
Distribution-layer maybe collapsed into the core-layer switches or removed completely
Collapsed core – no distribution
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Collapsed core – no distribution
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This design is most common in smaller implementations
Core switches act as all layers in the design For this design Ethernet runs must remain
within the distance limitations of the cable (100 Meters)
High-density chassis switches are used in this design
Collapsed core – no distribution or access
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Collapsed core – no distribution or access
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Trunks – will be necessary anywhere switches are interconnected
EtherChannels or port aggregation – This allows multiple switch connections to increase bandwidth between switches
Spanning tree – end devices ports should not run spanning tree. Ports connecting other switches must run it and be configured correctly including setting a correct primary and secondary root bridge
Configurations Concerns
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VTP – allows for centralized control of VLAN in your network
VLAN – How many? Make sure they are planned out ahead of time◦ Internet◦ Internet inside◦ Server farm◦ User VLANS (include all user devices that need
segmented i.e. VoIP)◦ OOB???
Configurations Concerns
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Most web-based applications today use a three tier design
Internet Layer - Web servers are used by the end users to access the application
Application layer – used to access the database layer and provide separation between the database and users. Also contains logic and access control for application
Database layer – contains data needed by application
Server Farm Design
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Server Farm Design
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There are generally two accepted methods in the design
Bridging – the lower interfaces of the upper layer are connected to the same VLAN as the upper interfaces of the layer beneath them
Routing – routers are placed between the layers
Server Farm Design
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Bridged Three-Tier Design
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The advantages of this design are simplicity and speed
Disadvantages are decreased security This has changed with the advances in
security devices (layer-2 firewalls)
Bridged Three-Tier Design
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Routed Three-Tier Design
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The advantages of this design are increased security
Disadvantages increases complexity and adds processing (which means latency)
Routed Three-Tier Design
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Is there any other issue that may need addressed in the design????
Server Farm Design
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Server Farm Design
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Can not easily manage the server remotely
Server Farm Design
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Can not easily manage the server remotely
Server Farm Design
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Every interface will need an IP address. In some server high-availability solutions, you’ll need a third IP address for each
VLAN. For example, IP multipathing requires a virtual IP address on each VLAN in addition to one for each physical interface.
Every IP address you assign may need a DNS entry (including virtual IP addresses).
Which interface is primary? Does the server need a default gateway? If so, where does it go? Can the server
support multiple defaults? How will this work? Web servers need a default gateway that points to the Internet. This will require your management VLAN to have specific routes on the servers.
How many physical network cards do you need in a server to support six Ethernet interfaces? Make sure you have enough. Extra interfaces are even better.
Will the servers have both interfaces active in each VLAN, or just one? Some server high-availability solutions require the switches to be configured a certain way, while others require different configurations. Work this out in a lab before you build your network.
Will your servers support remote Ethernet consoles? Will you need a dedicated network for this traffic?
Server Farm Design
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Server Farm Design
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With Virtual environment your access-layer switches are also virtualized
This will make the server network requirements more like a access-layer switch uplink
Multiple 10 Gb ports are common
Modern Virtual Server Environments