1.3 Design and Implement VNet Connectivity and Routing
📘Microsoft Azure Networking Solutions (AZ-700)
What is Azure Route Server?
Azure Route Server is a managed Azure service that allows dynamic routing between:
- Your Azure Virtual Network (VNet)
- Network Virtual Appliances (NVAs) such as firewalls or routers
- On-premises networks
- Azure VPN Gateway or ExpressRoute Gateway
It uses BGP (Border Gateway Protocol) to automatically exchange routes.
👉 Instead of manually creating and maintaining routes, Azure Route Server learns routes dynamically and updates them automatically.
Why Azure Route Server Is Needed
Without Azure Route Server:
- You must create User Defined Routes (UDRs) manually
- Route updates require manual changes
- Scaling becomes complex
- High risk of routing errors
With Azure Route Server:
- Routes are exchanged automatically
- Network changes are learned dynamically
- High availability is built-in
- Works seamlessly with NVAs and gateways
Key Concept: BGP (Border Gateway Protocol)
Azure Route Server uses BGP to share routing information.
What BGP Does:
- Advertises network prefixes
- Learns routes from connected devices
- Automatically updates routes when changes occur
In Azure Route Server:
- Azure Route Server acts as a BGP route reflector
- NVAs and gateways act as BGP peers
Where Azure Route Server Is Deployed
Azure Route Server is deployed inside a VNet, but in a dedicated subnet.
Required Subnet:
Subnet name: RouteServerSubnet
Subnet size: /27 or larger
⚠️ This subnet:
- Cannot host any other resources
- Is used only by Azure Route Server
Core Components of Azure Route Server
1. Azure Route Server
- Managed service
- Provides dynamic routing
- Highly available by default
2. BGP Peers
- Network Virtual Appliances (firewalls, routers)
- VPN Gateway
- ExpressRoute Gateway
3. Route Propagation
- Routes learned via BGP are automatically injected into:
- VNet route tables
- Subnets
Azure Route Server Architecture (Conceptual)
On-Prem Network
|
VPN / ER
|
Azure Route Server
|
NVA (Firewall)
|
Azure Workloads
Routes flow both directions using BGP.
Supported Routing Scenarios
Azure Route Server supports:
1. NVA Integration
- Firewalls (Azure Firewall, third-party firewalls)
- SD-WAN appliances
- Virtual routers
Routes learned from NVAs are automatically shared with:
- VNet subnets
- Gateways
2. Hybrid Connectivity
- On-premises networks
- VPN Gateway
- ExpressRoute Gateway
Azure Route Server exchanges routes between:
- On-premises
- Azure VNets
- NVAs
3. Active-Active Routing
- Multiple NVAs can connect
- BGP handles failover
- Traffic reroutes automatically
Azure Route Server vs User Defined Routes (UDRs)
| Feature | Azure Route Server | UDR |
|---|---|---|
| Routing type | Dynamic | Static |
| Uses BGP | Yes | No |
| Auto updates | Yes | No |
| Scalability | High | Limited |
| Failover support | Automatic | Manual |
👉 Exam tip:
If the question mentions dynamic routing, automatic updates, or BGP, the answer is Azure Route Server.
Supported Gateways
Azure Route Server works with:
- VPN Gateway
- ExpressRoute Gateway
⚠️ Important:
- Azure Route Server does not replace VPN or ExpressRoute
- It enhances routing intelligence
Route Exchange Behavior
Azure Route Server:
- Learns routes from BGP peers
- Advertises routes to:
- NVAs
- Gateways
- Subnets
What It Does NOT Do:
- Does not perform NAT
- Does not filter traffic
- Does not act as a firewall
High Availability and Resiliency
Azure Route Server:
- Is fully managed
- Runs in active-active mode
- No manual HA configuration required
BGP automatically:
- Detects failures
- Redirects traffic
Security Considerations
- Uses private IP addresses
- Traffic stays within Azure backbone
- Supports secure hybrid connectivity
- Works with NSGs and Azure Firewall
Limitations (Important for Exam)
- One Azure Route Server per VNet
- Requires dedicated subnet
- Supports IPv4 BGP only (exam relevant)
- Cannot be deployed in a peered VNet
When to Use Azure Route Server (Exam Scenarios)
Use Azure Route Server when:
- You want dynamic routing
- You use NVAs
- You have hybrid networks
- You want to avoid managing UDRs
- You need automatic failover
Do NOT use Azure Route Server when:
- Routing is simple and static
- No NVAs or hybrid connectivity is involved
Common Exam Keywords to Watch For
If you see these terms, think Azure Route Server:
- BGP
- Dynamic routing
- Route propagation
- NVA integration
- Automatic route updates
- Hybrid routing
Summary (Must Remember for AZ-700)
- Azure Route Server enables dynamic routing using BGP
- Deployed in a dedicated subnet
- Works with NVAs, VPN, and ExpressRoute
- Eliminates complex manual routing
- Built-in high availability
- Essential for advanced Azure networking designs
