Network Scaling : how to grow your Network Expansion

Network Scaling : how to grow your Network Expansion

Network Scalling is a very important concept in network design. A well-designed network controls traffic and limits the size of fault domains. A network design must include an IP addressing strategy, scalable and fast convergence routing protocols, appropriate layer 2 protocols and modular or clustered devices that can be easily updated to increase capacity. (how to grow your Network Expansion)
To support an enterprise network, the network designer must develop a strategy that allows the network to be available and can be scaled easily and efficiently .

Table of Contents

• Design that supports scalability
• Advanced network design requirements
• LAN redundancy
• Increase bandwidth
• Expansion of the access layer
• Adjust routing protocols
• OSPF
• EIGRP

Design that supports Scalability

In a basic network design strategy, the following recommendations are included:

• Use expandable modular equipment or grouped devices that can be easily upgraded to increase capacities. Device modules can be added to existing equipment to support new devices and features without the need for large-scale equipment updates. Some devices can be integrated into a cluster to function as a single device, to simplify administration and configuration.
• Design the hierarchical network to include modules that can be added, updated and modified as necessary, without affecting the design of other functional areas of the network. For example, create a separate access layer that can be expanded without affecting the distribution and core layers of the campus network.
• Create an IPv4 or IPv6 address strategy that is hierarchical . If IPv4 addressing is meticulously planned, the need to redirect the network to support additional users and services is avoided.
• Choose routers or multilayer switches to limit broadcast and filter other unwanted traffic on the network. Use Layer 3 devices to filter and reduce traffic to the network core.

Advanced network design requirements

As shown in Image 1, the most advanced network design requirements include the following:

• The implementation of redundant links in the network , between the essential devices and the access layer and core layer devices.
• The implementation of several links between the teams , either with link aggregation ( EtherChannel ) or with load balancing of the same cost to increase bandwidth. The combination of several Ethernet links in a single configuration with EtherChannel load balancing increases the available bandwidth. EtherChannel implementations can be used when, due to budget constraints, high-speed interfaces or fiber optic lines cannot be acquired.
• The implementation of wireless connectivity to allow mobility and expansion.
• The use of a scalable routing protocol and the implementation of features within that protocol to isolate routing updates and minimize the size of the routing table.

LAN Redundancy

For most organizations, network availability is critical to meet business needs. Redundancy is an important part of network design to prevent interruptions of network services by minimizing the possibility of a single point of failure. One method of implementing redundancy is to install duplicate equipment and provide failover services for essential devices.
Another method of implementing redundancy is through redundant routes. Redundant routes offer alternative physical routes for data to cross the network. In a switched network, redundant routes support high availability. However, due to the operation of the switches, redundant routes in a switched Ethernet network may cause logical loops in layer 2. For this reason, the tree expansion protocol ( STP ) is required.
The STP protocol allows the redundancy necessary to provide reliability, but eliminates switching loops. To do this, it provides a mechanism to disable redundant routes in a switched network until the route becomes necessary, for example, when a fault occurs. It is an open standards protocol, which is used in a switching environment to create a logical topology without loops.
In the next chapter "LAN redundancy", more details about LAN redundancy and STP operation are described.

Increase bandwidth

In the hierarchical network design, some links between access and distribution switches may need to process a greater amount of traffic than other links. As the traffic of several links converges on a single outbound link, a bottleneck may occur in that link .
Link aggregation allows the administrator to increase bandwidth between devices by creating a logical link composed of several physical links. As shown in Image 3, EtherChannel is a form of link aggregation that is used in switched networks.

EtherChannel uses the existing switch ports, therefore it is not necessary to incur additional costs to update the link to a faster and more expensive connection. The EtherChannel link looks like a logical link that uses an EtherChannel interface. Most configuration tasks are performed on the EtherChannel interface instead of on each individual port, which ensures configuration consistency across all links.
Finally, the EtherChannel configuration takes advantage of load balancing between the links that are part of the EtherChannel itself and, depending on the hardware platform, one or more load balancing methods can be implemented.

Expansion of the Access layer

The network should be designed to be able to expand network access for people and devices , as necessary. For the extension of access layer connectivity, wireless connectivity is increasingly important . The provision of wireless connectivity provides many advantages, such as increased flexibility, reduced costs and the ability to grow and adapt to the changing requirements of networks and businesses.

To communicate wirelessly, the terminals require a wireless NIC that incorporates a radio transmitter or receiver and the software driver necessary for it to work. As shown in Image 4, a wireless router or a wireless access point (AP) is also required for users to connect.

Adjust routing protocols

ISPs and business networks generally use more advanced routing protocols, such as link status protocols , due to their hierarchical design and the ability to scale to larger networks.

OSPF

Link state routing protocols, such as the OSPF (Open Shortest Path First) protocol , shown in Image 5, work well in larger hierarchical networks, where it is important to have rapid convergence. OSPF routers establish and maintain neighbor adjacencies with other OSPF routers connected.
When routers initiate an adjacency with neighbors, an exchange of Link-State updates begins . Routers reach a FULL adjacency state by synchronizing the views of their Link-State databases. With OSPF, Link-State updates are sent every time there are changes in the network.
OSPF is a popular link state routing protocol that can be adjusted in many ways. In the chapter “Setting and solving single area OSPF problems”, some of the more advanced features of OSPF configuration and troubleshooting are detailed.

In addition, OSPF supports a two-layer hierarchical design, or multi-area OSPF, shown in figure. All OSPF networks begin with an Area 0, also called a backbone area. As the network expands, other areas that are not backbone can be created. All non-backbone areas must be connected directly to area 0. In the chapter " Multi-area OSPF ", the benefits, operation and configuration of multi-area OSPF are presented.

 EIGRP

Another popular routing protocol in larger networks is the Enhanced Interior Gateway Routing Protocol (EIGRP). Cisco developed EIGRP as an exclusive vector distance routing protocol with enhanced capabilities. Although the EIGRP configuration is relatively simple, this protocol has broad and strong underlying features and options.

For example, EIGRP uses several tables, which are shown in above figure, to manage the routing process. EIGRP contains many functions that none of the other routing protocols have. It is an excellent choice for large multi-protocol networks in which Cisco devices are mainly used.
The "EIGRP" chapter describes the operation and configuration of the EIGRP routing protocol, while the chapter "Advanced configuration and troubleshooting of EIGRP" covers some of the most advanced EIGRP configuration options.