Cisco 3 - Switches Perrine - Brierley Page 15/10/2015 Module 5 Switches LAN Design LAN Switches

Cisco 3 - Switches Perrine - Brierley Page 25/10/2015 Module 5 LAN Design - Servers Workgroup –Provide file/print/application services to groups of users –Placed in IDF close to users Enterprise –Provide enterprise services such as DNS, , applications –Increasing trend to enterprise servers in organisations –Should be placed in MDF

Cisco 3 - Switches Perrine - Brierley Page 35/10/2015 Module 5 LAN Design - Availability Goal to maximise availability Throughput Response time Access to resources

Cisco 3 - Switches Perrine - Brierley Page 45/10/2015 Module 5 Layer 1 Design Copper medium? – CAT5, CAT5e, CAT6 UTP/STP Fibre? Position of MDF/IDF to create appropriate catchment areas

Cisco 3 - Switches Perrine - Brierley Page 55/10/2015 Module 5 Layer 2 Design Flow control, error detection & correction, reduce congestion Reduce collision domain size & effects of collisions Keep collision domains small – ideally fully switched full-duplex environment

Cisco 3 - Switches Perrine - Brierley Page 65/10/2015 Module 5 Layer 3 Design Controls traffic flow between network segments Logical addressing scheme to separate different network/workgroup functions Broadcast control

Cisco 3 - Switches Perrine - Brierley Page 75/10/2015 Module 5 Hierarchical Design Model Core layer – backbone – no packet manipulation Distribution layer – packet manipulation, interconnecting workgroups, Layer 3 switches, enterprise servers Access layer – closest to user/workgroup – hosts, switches, workgroup servers

Cisco 3 - Switches Perrine - Brierley Page 85/10/2015 Module 5 Switches

Cisco 3 - Switches Perrine - Brierley Page 95/10/2015 Module 5 NOTE: The following is Cisco’s logical idea of planning a LAN. Their design is an approach but not the only one. Medium & smaller companies will depend on the ideas of their people to come up with design criteria – this is where the Cisco planning criteria can be used. This chapter will give additional requirements & suggestions for your LAN design.

Cisco 3 - Switches Perrine - Brierley Page 105/10/2015 Module 5 First step in designing a LAN establish & document the goals of the design. It is based on: functionality –design must meet the job requirement – must work; connectivity with reasonable speed & reliability scalability – initial design should grow without any major chances to overall design adaptability – design toward the future (Frame Relay over ATM; SMDS, Switched Multi-megabit Data Service, to ATM) manageability – design to facilitate network monitoring & management Inter-network design seeks to provide the greatest availability for the least cost.

Cisco 3 - Switches Perrine - Brierley Page 115/10/2015 Module 5 One needs to consider the following in overall LAN design: function & placement of servers collision detection place devices to reduce the collision contention refers to excessive collisions on Ethernet caused by too many devices segmentation use bridges, switches & routers to separate collision domains note for bridges & switches; don’t forward collisions, but still belong to the broadcast domain bandwidth vs. broadcast domains bandwidth domain is everything associated with one port on a bridge /switch. All workstations within one bandwidth domain compete for the same LAN bandwidth resource.

Cisco 3 - Switches Perrine - Brierley Page 125/10/2015 Module 5 Under segmentation: bridges & switches are used results in multiple collision domains still a single broadcast domain Bandwidth domain is everything associated with one port on a bridge or switch. For Ethernet switches, a bandwidth domain is also known as a collision domain.

Cisco 3 - Switches Perrine - Brierley Page 135/10/2015 Module 5 Cisco’s design methodology: 1)Gather the users’ requirements & expectations organization’s history operational policies what their business is who has the authority to make decisions on network changes 2) Analyze requirements what are the voice & data requirements; which is in more demand; affects bandwidth requirements of the users 3) Design the layer 1,2,3 i.e. topology type of topology – star, extended star (most common; 802.3) cabling ( TIA/EIA-568-A); UTP; FIBER type of cabling determines the distance of the catchment area 4) Document the logical & physical network implementation

Cisco 3 - Switches Perrine - Brierley Page 145/10/2015 Module 5 Servers: Two distinct classes: enterprise server – supports all the users on the network by offering services ( , DNS) placed in the MDF workgroup server – applications for users placed in the IDF

Cisco 3 - Switches Perrine - Brierley Page 155/10/2015 Module 5 Cisco: between the MDF and IDF, the layer 2 LAN switches should have 100 Mbps or more allocated for these servers. Intranet versus the internet is that the public does not have access to the organization intranet. When layer 2 bridges or switches are used for segmentation, they create separate collision domains, and hence increase bandwidth to individual stations. A bandwidth domain is everything associated with one port on a bridge or switch.

Cisco 3 - Switches Perrine - Brierley Page 165/10/2015 Module 5 MDF – Main Distribution Facility HCC – Horizontal cross-connect Wiring closet where the horizontal cabling connects to a patch panel that is connected by backbone cabling to the MDF IDF – Intermediate Distribution Facility Used when a second wiring closed is needed because the hosts are outside of the 100 meter limit. Multiple catchment areas are formed. The IDF is connected to the MDF. IDF is connected to the MDF by using vertical cabling, also called the backbone cabling VCC – Vertical cross-connect Is used to interconnect the various IDFs to the central MDF. Fast Ethernet, cooper wire ( 100Base-TX) & fiber-optic (100Base-FX) is used to connect the MDF to the IDF.

Cisco 3 - Switches Perrine - Brierley Page 175/10/2015 Module 5 Layer 2 devices, bridges/switches purposes in the network is to provide: flow control error detection error correction reduce congestion

Cisco 3 - Switches Perrine - Brierley Page 185/10/2015 Module 5 Asymmetric Switching / Symmetric Switching 10 Mbps switch 10 Mbps 100 Mbps 10 Mbps switch

Cisco 3 - Switches Perrine - Brierley Page 195/10/2015 Module 5 In a pure switched LAN environment, the size of the collision domain is two hosts. Routers allows for segmentation of the LAN into unique physical & logical networks. Routers provide scalability because they can serve as firewalls for broadcasts.

Cisco 3 - Switches Perrine - Brierley Page 205/10/2015 Module 5 3-layer Model Core Distribution Access Other sites/Internet Campus Backbone Building Backbone

Cisco 3 - Switches Perrine - Brierley Page 215/10/2015 Module 5 3-layer Model Core Core implemented as WAN doesn’t perform any packet manipulation no ACLs, nor filtering were redundant paths are established load sharing & rapid convergence of routing protocols efficient use of bandwidth Other sites/Internet

Cisco 3 - Switches Perrine - Brierley Page 225/10/2015 Module 5 3-layer Model Distribution Core Distribution demarc between access & core layers ACLs are added; filtering; packet manipulation VLAN routing workgroup access to the core layer broadcast/multicast domain definition policy-based connectivity (what is acceptable traffic) where remote sites have access security Building backbone Campus backbone

Cisco 3 - Switches Perrine - Brierley Page 235/10/2015 Module 5 3-layer Model Access Access where local end users have access to network shared bandwidth switched bandwidth MAC-layer filtering microsegmentation isolate broadcast traffic from the workgroup ACLs & filtering LAN logical segmentation into functions

Cisco 3 - Switches Perrine - Brierley Page 245/10/2015 Module 5 Server Placement Enterprise Server Too much traffic for router 1 when enterprise server placed at access layer. 1 Core Distribution Access

Cisco 3 - Switches Perrine - Brierley Page 255/10/2015 Module 5 Server Placement Enterprise Server Less traffic for router 1 when enterprise server placed at distribution layer. 1 Core Distribution Access

Cisco 3 - Switches Perrine - Brierley Page 265/10/2015 Module 5 Server Placement Workgroup Server Workgroup server is placed at access layer of site where the largest concentration of users are located. 1

Cisco 3 - Switches Perrine - Brierley Page 275/10/2015 Module 5 Enterprise servers are placed at the highest layer in the hierarchy. Workgroup servers are placed nearest to the group that is using it.

Cisco 3 - Switches Perrine - Brierley Page 285/10/2015 Module 5 Cisco suggests the following equipment for physical design: core (routers) distribution (routers) access (routers)