Forum Discussion
Why do vpn/application gateways need to be in their subnet?
Normally in a network, your default gateway would be in the same subnet (well, mine is at least), but I can't figure out why azure requires your gateway needs to be in their own subnet, with like 3 spaces?
1 Reply
May related to:
1. Isolation for Managed Services
- Azure VPN and Application Gateways are managed services with their own control plane.
- By placing them in a dedicated subnet, Azure ensures clean separation between gateway infrastructure and user workloads.
- This isolation helps prevent conflicts with other resources and simplifies updates, scaling, and diagnostics.
2. Reserved IPs and Internal Routing
- Gateways often reserve multiple IP addresses in their subnet for internal components (e.g., health probes, load balancer front ends).
- Azure needs predictable space to allocate these resources without overlapping with your VMs or services.
3. Security and Policy Enforcement
- Dedicated subnets allow you to apply Network Security Groups (NSGs) and User Defined Routes (UDRs) specifically tailored to gateway traffic.
- This minimizes the risk of misconfigured rules affecting unrelated resources.
4. Operational Constraints
- Azure blocks deployment of other resources in gateway subnets to avoid interference.
