VPN Gateway Active-Active

Question

I have some queries about the VPN gateway and need help here.

• I have VPN Gateway use active-active mode disabled. With this mode my onprem can talk with the vnet. and BGP is connected. When i try change set active-active mode to enable why the existing BGP is changed from connected to connecting so my onprem can't reach to the vnet?
• I also have another VPN gateway with no BGP enabled on the VPN Gateway, Connection and Local Network Gateway. Currently i have 6 connection and all is connected. Now i want to enable the BGP for 2 connection, this mean i must enable the BGP on VPN Gateway side. When i enable the BGP in VPN gateway and enable BGP for 2 connection and 2 local network gateway, will existing 4 connection will not impacted (all existing 4 connection still connected)?

Answer 1

When you enable Active-Active mode on an Azure VPN Gateway, the gateway transitions from a single public IP with one active instance to two active instances, each with its own public IP. This change disrupts the existing BGP session because your on-premises router needs to recognize the new setup and establish BGP peering with both instances. The existing BGP connection moves from "Connected" to "Connecting" because your on-premises router may still be trying to establish a session with the old single-instance setup. To fix this, ensure your on-premises router is configured to support two BGP peers (one for each gateway instance) and update your VPN device to establish connections with both IPs of the active-active setup.

For your second scenario, enabling BGP on the VPN Gateway and selectively enabling it for two out of six connections should not impact the existing four non-BGP connections. Azure allows BGP and non-BGP connections to coexist on the same VPN Gateway. However, once BGP is enabled, the two BGP-enabled connections will begin exchanging dynamic routes, while the remaining four connections will continue using static routes. Ensure that your routing policies do not unintentionally override static routes with BGP-learned routes, which could affect traffic flow.

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hth

Marcin