Network Topologies

Useful in planning a new network

Physical layout of a building or campus

Assists in understanding signal flow

Troubleshooting problems

Star/Hub and Spoke

Used in most large and small networks

All devices are connected to a central device

Switched Ethernet networks

The switch is in the middle

Mesh

Multiple links to the same place

Fully connected
Partially connected

Redundancy, fault-tolerance, load balancing

Used in wide area networks (WANs)

Fully meshed and partially meshed

Hybrid

A combination of one or more physical topologies

Most networks are a hybrid

Spine and Leaf Architecture

Each leaf switch connects to each spine switch

Each spine switch connects to each leaf switch

Leaf switches don’t connect to each other

Same for spine switches

Top-of-rack switching

Each leaf is on the “top” of a physical network rack
May include a group of physical racks

Advantages

Simple cabling
Redundant
Fast

Disadvantages

Additional switches may be costly

Point-to-point

One-to-one connection

Older WAN links

Point to point T-1

Connections between buildings

Network Architectures

Three-tier architecture

Core

The “center” of the network
Web servers, databases, applications
Many people need access to this

Distribution

A midpoint between the core and the users
Communication between access switches
Manage the path to the end users

Access

Where the users connect
End stations, printers

Collapsed Core

A two-tier model

Simplify the three-tier architecture
A good fit for smaller organizations

Combine Core and Distribution layers

Collapse together

Differences over three-tier

Simpler to design and support
Less expensive to implement
Not as resilient

Traffic Flows

Traffic flows within a data center

Important to know where traffic starts and ends

East-west

Traffic between devices in the same data center
Relatively fast response times

North-south traffic

Ingress/egress to an outside device
A different security posture than east-west traffic