A Metropolitan Area Network, or MAN, connects multiple local area networks across a city, campus group, industrial zone, or regional business district. A clear MAN diagram helps planners, engineers, managers, and vendors understand how buildings, data centers, routers, switches, fiber links, wireless backhaul, and service provider connections work together.
TLDR: A MAN diagram should show the major sites, backbone connections, network devices, service provider links, and redundancy paths across a metropolitan area. For example, a city government connecting 12 municipal buildings might use two data centers, fiber rings, and backup wireless links to maintain 99.9% service availability. The most useful diagram is not overloaded with every cable; it highlights structure, traffic flow, resilience, and ownership boundaries. A good approach is to start with locations, add core devices, then layer in links, labels, security zones, and failover paths.
Understanding the Purpose of a MAN Diagram
Before drawing begins, the network planner should define why the diagram is being created. A MAN diagram may support a new deployment, document an existing environment, explain bandwidth requirements, or help diagnose performance and redundancy issues. The intended audience affects the level of detail. An executive version may show only sites and major links, while an engineering version may include interfaces, VLANs, IP ranges, circuit IDs, routing protocols, and failover priorities.
A metropolitan area network often includes multiple LANs, a high speed backbone, carrier services, and centralized resources such as cloud gateways, data centers, security appliances, and monitoring systems. The diagram should make these relationships easy to understand at a glance.
Step 1: Identify the Geographic Scope
The designer should first list every location that belongs in the MAN. These may include headquarters, branch offices, universities, hospitals, municipal buildings, warehouses, transport hubs, or data centers. Each location should be identified with a short, consistent name, such as City Hall, Data Center A, or North Campus.
At this stage, it is useful to group locations by district or function. For example, a healthcare MAN may group sites into hospitals, clinics, administrative offices, and disaster recovery facilities. If physical distance matters, the diagram can use a simplified city map style. If topology matters more than geography, a logical layout may be better.
Step 2: Choose the Diagram Type
A MAN can be drawn in several ways. The planner should choose the format that best matches the purpose:
- Physical diagram: Shows buildings, cables, towers, fiber paths, cabinets, and carrier handoff points.
- Logical diagram: Focuses on routers, switches, VLANs, subnets, routing, firewalls, and traffic flow.
- Hybrid diagram: Combines city level locations with key logical components.
- High level architecture diagram: Presents the MAN for leadership, budgeting, or vendor discussion.
For most planning documents, a hybrid diagram is the most practical choice. It shows key sites and links while still including core devices, redundancy, and security zones.
Step 3: Place the Main Sites and Network Core
The diagram should begin with the most important nodes. Typically, these are the central data center, secondary data center, internet edge, cloud gateway, or network operations center. These core elements should be placed near the center or top of the diagram because other sites depend on them.
Next, the designer should add the connected locations around the core. The layout should be clean and consistent. Sites to the north, south, east, and west of a city may be arranged geographically, while departments or campuses may be arranged by business function. Each site should contain only the most relevant devices, such as an edge router, distribution switch, firewall, or wireless bridge.
Step 4: Add Backbone Links and Access Connections
After the sites are placed, the main connectivity should be drawn. A MAN commonly uses fiber optic links, Ethernet metro services, MPLS, leased lines, or licensed wireless backhaul. The diagram should distinguish between backbone links and local access links by using different line styles, colors, or thicknesses.
For example, a 10 Gbps fiber ring might be shown with a thick blue line, while 1 Gbps branch connections might use thinner gray lines. Backup wireless links could be shown as dotted orange lines. If the organization leases circuits from a carrier, the provider edge should be clearly marked so that ownership and support responsibility are obvious.
- Solid lines can represent primary wired connections.
- Dotted lines can represent backup or wireless paths.
- Thicker lines can represent higher bandwidth links.
- Color coding can separate providers, regions, or security zones.
Step 5: Show Redundancy and Failover Paths
One of the most important features of a MAN diagram is redundancy. Metropolitan networks often support critical services, so the diagram should show how traffic continues if a link or device fails. Ring topologies, dual homed branches, paired firewalls, and secondary internet connections should be easy to identify.
For instance, a university MAN may connect six campuses through a fiber ring. If one fiber segment is cut, traffic can reverse direction around the ring. In the diagram, arrows or labels can indicate the failover path and routing behavior. If failover is automatic, the label might mention OSPF dynamic routing, BGP failover, or spanning tree blocked path.
Step 6: Add Devices, Labels, and Technical Details
Once the topology is clear, the designer should add device symbols and labels. Common MAN components include core routers, aggregation switches, branch routers, firewalls, intrusion prevention systems, wireless towers, optical transport equipment, and monitoring servers. Each item should be labeled clearly but briefly.
Useful labels may include:
- Device names: Such as RTR DC1 01 or FW Internet Edge A.
- Bandwidth: Such as 10 Gbps, 2 Gbps, or 500 Mbps backup.
- IP ranges: Where necessary for engineering diagrams.
- Provider names: Especially when multiple carriers are involved.
- Security zones: Such as internal, guest, public, management, and DMZ.
The diagram should avoid excessive detail. If every switchport, cable number, and VLAN is shown on one page, the result may become unreadable. A better method is to create a high level MAN diagram and separate detailed diagrams for each major site.
Step 7: Use Standard Symbols and a Legend
Consistent symbols make the diagram easier to read. Routers, switches, firewalls, cloud services, servers, and wireless towers should each have distinct icons. A legend should explain all line styles, colors, abbreviations, and special markings. This is especially important when the diagram is shared with nontechnical stakeholders.
A professional MAN diagram also includes a title block or information area with the version number, date, author, project name, and approval status. These details help prevent confusion when multiple versions are circulated during planning or maintenance.
Step 8: Validate the Diagram
After the draft is complete, it should be reviewed by network engineers, facilities staff, security teams, and service providers. The reviewer should confirm that site names, link speeds, circuit IDs, device roles, redundancy paths, and provider boundaries are accurate. If the diagram supports an active network, it should also be compared with configuration files, monitoring tools, and inventory records.
Validation is not just a technical step. It also helps reveal design issues. For example, a planner may discover that 70% of traffic from branch offices depends on a single data center router, creating a bottleneck. The visual diagram can make that risk much easier to notice than a spreadsheet.
Common Mistakes to Avoid
- Overcrowding the diagram: Too many labels and devices can hide the main topology.
- Ignoring redundancy: Backup paths must be visible, not left to assumptions.
- Mixing physical and logical details without structure: A hybrid diagram should still be organized.
- Using unexplained colors: Every color and line style should appear in the legend.
- Forgetting provider boundaries: Carrier handoffs and managed services should be clearly marked.
Best Practices for a Clear MAN Diagram
A strong MAN diagram is simple, accurate, and layered. It should show the metropolitan scope without overwhelming the reader. The central backbone should be visually prominent, while secondary details should support the main story. When multiple audiences need different information, separate diagrams are usually better than one crowded master diagram.
The planner should also keep the diagram updated. Metropolitan networks change as new buildings, cloud services, security requirements, and bandwidth demands are added. A diagram that is reviewed quarterly or after every major change remains useful for troubleshooting, compliance, budgeting, and disaster recovery.
FAQ
What is a MAN diagram?
A MAN diagram is a visual representation of a metropolitan area network. It shows how multiple sites across a city or region are connected through backbone links, routers, switches, security devices, and service provider connections.
What should be included in a MAN diagram?
It should include major locations, core devices, access devices, backbone links, internet or cloud connections, provider boundaries, link speeds, redundancy paths, and a legend explaining symbols and line styles.
Should a MAN diagram be physical or logical?
It depends on the purpose. A physical diagram is useful for cable routes and facilities planning, while a logical diagram is better for routing, security, and traffic flow. Many organizations use a hybrid version.
How detailed should the diagram be?
The diagram should be detailed enough to explain the network clearly but not so detailed that it becomes unreadable. Site level details, such as individual switchports, are often better placed in separate diagrams.
How often should a MAN diagram be updated?
It should be updated after any major network change, such as a new site, upgraded link, replaced router, or changed provider circuit. Many teams also review it on a quarterly basis.
