Point-to-Site Azure VPN Interesting Traffic

FunMum 140 Reputation points
2025-08-27T17:59:29.2166667+00:00

Hello,

We have Point-to-Site Clients that had deployed both Synapse (sql.azuresynapse.net) and SQL (sqlsvr.database.windows.net). The Azure PAAS Services are configured for external access. The external access is whitelisted by IP. Is there a way to direct the Azure PAAS Service external ip to go through the P-to-S connection as opposed to through the clients ISP public ip (since P-to-S is running split tunnel)? Is there a way to direct the PAAS external IP to go through the Azure P-to-S connection?

Azure VPN Gateway
Azure VPN Gateway

An Azure service that enables the connection of on-premises networks to Azure through site-to-site virtual private networks.

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Answer accepted by question author
Michele Ariis 7,315 Reputation points MVP Volunteer Moderator
2025-08-27T18:59:04.7466667+00:00

Hi, with P2S split-tunnel, you can't reliably route only traffic to public PaaS services (e.g. *.database.windows.net / .azuresynapse.net) via VPN: the client doesn't support split tunneling for FQDNs and public IPs change, so static routes break. Correct solutions: 1) Private Link (recommended): Create Private Endpoints for SQL and Synapse, connect the private DNS zones (privatelink.), have P2S clients resolve these FQDNs to the private IPs in the VNet; no allowlists on public IPs. 2) Force-tunnel the entire Internet via Azure and perform SNAT with Azure Firewall: publish the routes 0.0.0.0/1 and 128.0.0.0/1 to clients, UDR from GatewaySubnet→Firewall and back Firewall→Virtual network gateway; then allowlist the firewall's public IP. Avoid: Try to “push” only SQL/Synapse over the VPN while manually maintaining public IPs.

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