CONTROL PLANE AND DATA PLANE SEPARATION USING ROUTE REFLECTOR AND HIGH DENSITY SWITCH

 

WHAT IS CONTROL PLANE

Control Plane is responsible for decision making in the network. It does not forward real traffic.

Its main jobs are:
- Learning routes
- Exchanging routing information
- Selecting best paths
- Sharing routes with other routers

In this design, Route Reflectors (RR-1 and RR-2) handle the control plane.

ROLE OF ROUTE REFLECTOR

Route Reflector works as the brain of the network.

It performs:
- Receives routes from edge routers
- Selects best path using BGP logic
- Reflects routes to other routers

Very important point:
Route Reflector DOES NOT modify attributes like:
- Next-hop
- MED
- Local preference
- AS path

RR only reflects routes as they are.

Because next-hop is not changed, traffic does NOT pass through the Route Reflector.

This is the main reason RR can safely be used only for control plane.

WHY RR IS GOOD FOR CONTROL PLANE

- No packet forwarding load
- No data traffic passes through RR
- CPU and memory remain stable
- Scales very well in large networks
- Ideal for EVPN and large BGP fabrics

WHAT IS DATA PLANE

Data Plane is responsible for actual traffic forwarding.

It handles:
- User traffic
- Application traffic
- East-West traffic
- North-South traffic

Data plane devices forward packets based on routing information received from the control plane.

ROLE OF HIGH DENSITY SWITCH

The switch is used as the data plane device.

It provides:
- Hardware-based forwarding (ASIC)
- High throughput
- Low latency
- Line-rate packet switching

Because RR does not change next-hop, traffic directly flows through the switch without touching RR.

REAL TIME EXAMPLE

Assume R1 wants to send traffic to R4.

Step 1:
R1 advertises its route to the Route Reflector.

Step 2:
RR processes the route and reflects it to R2, R3, and R4.

Step 3:
RR does NOT change next-hop or any BGP attribute.

Step 4:
R1 sends traffic based on the learned next-hop.

Step 5:
Traffic flows directly through the switch to R4.

Important:
Traffic never goes to the Route Reflector. Only routing updates go to RR.

WHY THIS DESIGN IS VERY GOOD

- Clean separation of control and data plane
- No traffic load on Route Reflector
- Faster packet forwarding
- High scalability
- Easy troubleshooting
- Best suited for EVPN MPLS (In case of large ISP with iBGP)

SIMPLE UNDERSTANDING

Route Reflector = Brain
Switch = Muscle
Routers = Entry and Exit points

This is why using a switch for data plane and RR for control plane is a perfect and scalable design for modern data centers.