Computing resource service providers provide computing resources to customers in a multi-tenant environment. Communication between resources in a customer's virtual private network and an internet gateway in the form of data packets may be intercepted and processed by a firewall to help ensure that traffic entering or exiting the customer's virtual private network is valid and secure. These data packets are intercepted and analyzed by a service in a separate virtual private network and filtered in a way such that data packets with the same networking flow are provided to the same firewall servers so that firewall rules applied to the data packets are consistent.