Collective Remote Attestation (CRA) is a well-established approach where a single Verifier attests the integrity of multiple devices in a single execution of the challenge-response protocol. Current CRA solutions are well-suited for Internet of Things (IoT) networks, where the devices are distributed in a mesh topology and communicate only with their physical neighbours. Recent advancements on low-energy protocols, though, enabled the IoT devices to connected to the Internet, thus disrupting the concept of physical neighbour. In this paper, we propose HolA (Holistic and Autonomous Attestation), the first CRA scheme designed for Internet-like IoT networks. HolA provides defence against attacks targeting both the nodes and the network infrastructure. We deployed HolA on both a network of real devices (i.e., 5 Raspberry Pis) and a simulated environment (i.e., 1M devices in an Omnet++ network). Our results demonstrate that HolA can resist against a disruptive attacker that compromises up to half of the network devices and that tampers with network traffic. HolA can verify the integrity of 1M devices in around 12 s while the state-of-the-art requires 71 s. Finally, HolA requires 7 times less memory per device compared with the state-of-the-art.