+**Issues with User-defined Inbound TCP rules**: [Network Security Groups (NSGs)](../virtual-network/network-security-groups-overview.md) are implemented as a [Stateful firewall](https://en.wikipedia.org/wiki/Stateful_firewall?oldformat=true). However, due to current platform limitations, user-defined rules that affect inbound TCP flows are implemented in a stateless fashion. Due to this, flows affected by user-defined inbound rules become non-terminating. Additionally byte and packet counts are not recorded for these flows. Consequently the number of bytes and packets reported in NSG Flow Logs (and Traffic Analytics) could be different from actual numbers. This can be resolved by setting the [FlowTimeoutInMinutes](/powershell/module/az.network/set-azvirtualnetwork) property on the associated virtual networks to a non-null value. Default stateful behavior can be achieved by setting FlowTimeoutInMinutes to 4 minutes. For long running connections, where you do not want flows disconnecting from a service or destination, FlowTimeoutInMinutes can be set to a value upto 30 minutes.
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