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azure outbound data flow has stopped

PAdministrator 0 Reputation points
2025-09-10T08:53:15.88+00:00

We have a S2S VPN tunnel between a Meraki Firewall and Azure. Egress data from Azure suddenly stopped working at 2am. We have checked the VPN tunnel is up. We have reset both ends of the Azure and Meraki VPN tunnel and it came up straight away. We can see inbound traffic from Meraki going into Azure over the VPN Tunnel. We can browse the internet from the Azure hosts but cannot seem to connect over the VPN tunnel.

Azure Virtual WAN
Azure Virtual WAN
An Azure virtual networking service that provides optimized and automated branch-to-branch connectivity.

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  1. Ravi Varma Mudduluru 2,690 Reputation points Microsoft External Staff Moderator
    2025-09-10T10:43:24.91+00:00

    Hello @PAdministrator,

    Thanks for reaching out to Microsoft Q&A. 

    I understand that you're experiencing an issue where the outbound data flow from Azure over your Site-to-Site (S2S) VPN tunnel to your Meraki Firewall has completely stopped. Given that you've already confirmed the VPN tunnel is up and have reset it on both ends,Here are some steps you can try to troubleshoot the connectivity issue:

    • Please verify that the NSGs associated with your Azure Virtual Network (VNet) are not blocking outbound traffic to the Meraki Firewall. Ensure both inbound and outbound rules allow the necessary connections.
    • Review firewall rules on both Azure and Meraki sides to ensure outbound traffic from Azure to Meraki is not being blocked. Sometimes, rule updates or misconfigurations can unintentionally restrict traffic.
    • Check the Azure route table to confirm that outbound traffic is correctly routed to the Meraki Firewall over the VPN. Missing or incorrect routes can cause traffic to drop silently.
    • Review diagnostic logs from both Azure (GatewayDiagnosticLog, TunnelDiagnosticLog, RouteDiagnosticLog) and Meraki. These logs often reveal whether traffic is being dropped or misrouted.
    • Double-check the VPN settings on both ends. Even minor mismatches in configuration (e.g., IP ranges, shared keys, encryption settings) can affect specific traffic flows.

    Supporting Document:

    https://documentation.meraki.com/MX/Site-to-site_VPN/IPsec_VPN_Lifetimes

    Check the document for more understanding: https://learn.microsoft.com/en-us/azure/vpn-gateway/vpn-gateway-about-vpn-devices

    Kindly let us know if the above helps or you need further assistance on this issue.

    Please "Accept the Answer" if the information helped you. This will help us and others in the community as well.

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