📘Cisco DevNet Associate (200-901 DEVASC)
Purpose:
The management plane is responsible for managing and configuring the network device. It’s how network administrators interact with the device.
Key Functions:
- Allows administrators to access the device via interfaces like:
- CLI (Command-Line Interface)
- Web GUI
- APIs (e.g., REST APIs)
- Handles device monitoring and logging.
- Supports security and authentication (e.g., SSH, TACACS+, RADIUS).
- Stores and manages device configurations.
Example in IT environment:
- When a network engineer logs into a switch to change VLAN settings, that activity is happening in the management plane.
- When a monitoring tool like Cisco DNA Center queries a router for CPU or memory usage, it communicates via the management plane.
Key Points to Remember:
- Only administrators interact with this plane.
- It does not directly move user traffic.
- Critical for troubleshooting and network monitoring.
2. Control Plane
Purpose:
The control plane is responsible for deciding how traffic should flow in the network. It builds and maintains the routing and switching tables.
Key Functions:
- Runs network protocols like:
- Routing: OSPF, EIGRP, BGP
- Switching: STP (Spanning Tree Protocol)
- Path selection: choosing the best route for traffic
- Maintains routing tables and MAC address tables.
- Exchanges network information with other devices.
Example in IT environment:
- When a router learns about a new network from a neighbor router via OSPF, this is the control plane working.
- When a switch calculates the loop-free topology using STP, that is control plane activity.
Key Points to Remember:
- Control plane builds the decision logic for traffic.
- Traffic decision: “Where should this packet go?”
- Runs protocols in the background automatically.
3. Data Plane (Forwarding Plane)
Purpose:
The data plane is responsible for actually forwarding the traffic based on the decisions made by the control plane. It is the “workhorse” of the device.
Key Functions:
- Moves packets from input interface to output interface.
- Uses routing tables, MAC tables, and ACLs created by the control plane.
- Handles packet switching and forwarding at high speed.
- Can apply QoS, firewall rules, or NAT to traffic.
Example in IT environment:
- When a packet comes into a router on interface GigabitEthernet0/1 and is sent out via GigabitEthernet0/2, the data plane is forwarding that packet.
- When a switch forwards traffic within the same VLAN, it is the data plane doing the work.
Key Points to Remember:
- Moves user traffic in real-time.
- Works very fast; usually implemented in hardware (ASICs) for efficiency.
- Decisions come from the control plane, but execution is the data plane’s job.
Quick Comparison Table
| Plane | Who Uses It? | What It Does | Example IT Action |
|---|---|---|---|
| Management | Admins / Monitoring Tools | Configures and monitors the device | Logging into switch via CLI |
| Control | Device (internally) | Decides how traffic flows, builds tables | OSPF routing, STP topology calculation |
| Data | Device (hardware) | Forwards packets based on control plane decisions | Sending packets from one interface to another |
Exam Tips
- Remember the flow:
- Management plane = configure/manage device
- Control plane = decide where traffic goes
- Data plane = forward the traffic
- Planes can interact but have separate roles:
- Example: Management plane may trigger changes in control plane (update routing), which affects data plane (traffic forwarding).
- Common Exam Question Patterns:
- “Which plane handles OSPF routing?” → Control Plane
- “Which plane forwards packets?” → Data Plane
- “Which plane lets you SSH into a router?” → Management Plane
