Network segmentation is the practice of dividing a LAN into smaller, logical units called subnets or VLANs. This can improve the performance, security, and manageability of your network, as well as reduce costs and complexity. In this article, you will learn how to design a LAN for effective network segmentation, using some basic principles and tools.
Before you start designing your LAN, you need to understand your network requirements, such as the number and type of devices, the bandwidth and latency needs, the security and compliance policies, and the budget and resources available. You can use various methods to gather this information, such as interviews, surveys, audits, or network analysis tools. Based on your network requirements, you can determine the optimal size, structure, and configuration of your subnets or VLANs.
As this article states, identifying scope is fundamental. You need to identify your need, and then accommodate for future expansion. You can gauge what this demand is with relative data: Size of site, Amount of supported users, Departments, Planned Scalability. You can organize your subnets according to a standard design for easy recognition. Then standardize VLAN usage across layer 3 for your layer 2 networks, for once again, easy recognition. All these factors help determine how to lay the groundwork for your network to come and how to build a unified standard across a WAN Once this network is set in place? It will be much more difficult to fundamentally change it. Which is why getting it right the first time is paramount. ??
The next step is to choose the network devices and topology that will support your network segmentation. You will need routers, switches, firewalls, and other devices that can create and manage subnets or VLANs, as well as provide routing, switching, filtering, and monitoring functions. You will also need to decide how to connect these devices, using a logical topology that reflects the physical layout and the logical relationships of your subnets or VLANs. You can use various topologies, such as star, ring, bus, mesh, or hybrid, depending on your network requirements and preferences.
Investing in hardware that is scalable is really important for this. Make sure that the hardware supports what protocols, and throughput you need. In addition, purchase hardware that is still under active support. Avoid extended support when possible, to avoid quick turnaround on EOL replacement. Network design needs to be laid out prior to implementation. It's a lot to cover, but determine how to segment VLAN's, Subnets, implement a network hardware naming scheme, employ standardized configuration deployments for as little drift as possible. Implement the design one piece at a time and test each piece as you go. Verify full connectivity afterward once each piece has been individually verified.
Once you have chosen your network devices and topology, you need to assign IP addresses and subnet masks to your subnets or VLANs. This will allow you to identify and communicate with each subnet or VLAN, as well as control the traffic flow and routing between them. You can use either IPv4 or IPv6 addresses, depending on your network requirements and compatibility. You can also use various subnetting techniques, such as classful, classless, or variable length subnet masking, to optimize the use of your IP address space and avoid wasting or overlapping addresses.
If you are a small office? You can probably get away with simple classful subnetting. /24 etc. In addition a small centralized DHCP server, DNS server etc. For large enterprise networks? You will start recognizing the need for properly layered classless subnetting. /25, /17, /29, /27 etc (VLSM). As you scale you will need DHCP helpers throughout your WAN to help point DHCP traffic to a centralized server as you can't have conflicts. Properly planning your networks and implementing them in a methodical manner helps improve network design and transparency from an engineering standpoint.
After you have assigned your IP addresses and subnet masks, you need to configure your network devices and protocols to enable and support your network segmentation. You will need to set up the interfaces, ports, routing tables, access control lists, VLAN tags, and other parameters on your routers, switches, firewalls, and other devices. You will also need to choose and configure the protocols that will facilitate the communication and coordination of your subnets or VLANs, such as TCP/IP, DHCP, DNS, ARP, ICMP, OSPF, RIP, STP, and others.
Considering the security for the LAN is also very important for the survival of the organization. Today, many LAN users choose a wireless LAN (WLAN), which uses wireless signals such as Wi-Fi to connect to network devices. This method may have security risks. In the case of WLAN setup, malicious actors can perform evil twin attacks, where a wireless access point is created to impersonate a legitimate LAN access point and trick users into connecting. Using strong encryption and a VPN can help reduce the risks of an evil twin attack.
The final step is to test and troubleshoot your network segmentation, to ensure that it works as intended and meets your network requirements. You can use various tools and methods to test and troubleshoot your network segmentation, such as ping, traceroute, ipconfig, ifconfig, netstat, nmap, wireshark, and others. You should check for any errors, conflicts, misconfigurations, or security issues that may affect the performance, reliability, or security of your network segmentation. You should also document and update your network design and configuration, as well as monitor and maintain your network segmentation regularly.
As you implemented your networks, you should have been individually verifying connectivity as you go along. This will allow you to help isolate the issue from the get-go. In addition, it improves the odds of standing up a fully functional network from the beginning. If you did not? Then you have to start big and go small. Test connectivity to sites -> Test intra-site connectivity -> Test Client Connectivity and identify problematic configurations. Tools: Traceroute, Pathping, Ping, Syslog etc. More often than not, it won't work perfectly the first time. But have a fundamental understanding of how to troubleshoot your network will go hand in hand with your career, so make sure this is something you feel comfortable doing.