Which of the following are commonly used methods for segmentation?

Segmentation is a security strategy used to divide a network into smaller, isolated sections to enhance security and control access to sensitive data, particularly in compliance with standards like PCI DSS. Firewalls and router configurations are fundamental tools for implementing this strategy. Firewalls can establish rules that determine what data can travel between different segments of the network, thereby preventing unauthorized access or data leaks.

Router configurations can also support segmentation by managing traffic between different network segments, defining pathways and controlling data flow based on preset rules. When effectively configured, these devices create barriers between sensitive areas of the network and other parts, thus securing cardholder data from potential threats.

The other options mentioned play different roles in security but are not primarily focused on segmentation. Virtual Private Networks (VPNs) and encryption are more about securing data in transit rather than segmenting networks. Cloud storage solutions focus on data storage rather than managing network traffic or access, and single sign-on systems streamline user access across applications but do not provide network segmentation. Hence, firewalls and router configurations are the most relevant methods for achieving effective segmentation in a network.