Network Design
11.4 Router Hardware
11.4.1 Router Requirements
Switches are not the only component of a network that come with a variety of features. Your choice of router is another very important decision. Routers play a critical role in networking by connecting homes and businesses to the internet, interconnecting multiple sites within an enterprise network, providing redundant paths, and connecting ISPs on the internet. Routers can also act as a translator between different media types and protocols. For example, a router can accept packets from an Ethernet network and re-encapsulate them for transport over a serial network.
11.4.2 Cisco Routers
Branch Routers
Network Edge Routers
Service Provider Routers
Industrial
11.4.3 Router Form Factors
Like switches, routers also come in many form factors. Network administrators in an enterprise environment should be able to support a variety of routers, from a small desktop router to a rack-mounted or blade model.
Switch Hardware
Campus LAN Switches
Cloud-Managed Switches
Data Center Switches
Service Provider Switches
Virtual Networking
Switch Form Factors
Fixed configuration switches
Modular configuration switches
Stackable configuration switches
Thickness
Port Density
Cisco Catalyst 3850 Switches
Catalyst 9400 Switch
11.3.5 Power over Ethernet
Switch
click to edit
IP Phone
WAP
Cisco Catalyst 2960-C
11.1 Hierarchical networks
11.1.2 The Need to Scale the Network
Scaling a network is necessary to meet business growth, support more users and devices, integrate new technologies, ensure continuous availability, and maintain performance
11.1.3 Borderless Switched Networks
enable secure, reliable, and accessible connectivity anytime, anywhere, and on any device
11.1.4 Hierarchy in the Borderless Switched Network
Creating a boundaryless switched network requires robust design principles to ensure availability, flexibility, security, and manageability
11.1.5 Access, Distribution, and Core Layer Functions
Access layer connects users and devices directly
Distribution layer handles the interconnection and network policies between access and core
Core layer ensures high speed and reliability in data transmission between network segments
11.1.7 Role of Switched Networks
Switched LANs offer greater flexibility, traffic management, support for wireless networking, IP telephony, and mobility services
11.2 Scalable Networks
11.2.1 Design for Scalability
11.2.2 Plan for Redundancy
11.2.3 Reduce Failure Domain Size
11.2.4 Increase Bandwidth
11.2.5 Expand the Access Layer
11.2.6 Tune Routing Protocols
Redundant Links
Implement redundant links in the network between critical devices and between access layer and core layer devices.
Multiple Links
Implement multiple links between equipment, with either link aggregation (EtherChannel) or equal cost load balancing, to increase bandwidth.
Scalable Routing Protocol
Use a scalable routing protocol and implement features within that routing protocol to isolate routing updates and minimize the size of the routing table.
Wireless Connectivity
Implement wireless connectivity to allow for mobility and expansion.
For many organizations, the availability of the network is essential to supporting business needs. Redundancy is an important part of network design.
Another method of implementing redundancy is redundant paths, as shown in the figure above. Redundant paths offer alternate physical paths for data to traverse the network
A well-designed network not only controls traffic, but also limits the size of failure domains. A failure domain is the area of a network that is impacted when a critical device or network service experiences problems.
Edge Router
AP1
S1
S2
S3
In hierarchical network design, some links between access and distribution switches may need to process a greater amount of traffic than other links.
As traffic from multiple links converges onto a single, outgoing link, it is possible for that link to become a bottleneck.
The network must be designed to be able to expand network access to individuals and devices, as needed. An increasingly important option for extending access layer connectivity is through wireless.
Providing wireless connectivity offers many advantages, such as increased flexibility, reduced costs, and the ability to grow and adapt to changing network and business requirements.
Advanced routing protocols, such as Open Shortest Path First (OSPF), are used in large networks
OSPF is a link-state routing protocol. As shown in the figure, OSPF works well for larger hierarchical networks where fast convergence is important. OSPF routers establish and maintain neighbor adjacencies with other connected OSPF routers.
OSPF routers synchronize their link-state database. When a network change occurs, link-state updates are sent, informing other OSPF routers of the change and establishing a new best path, if one is available.