Networking Equipment
This domain covers how network devices are configured, segmented, and secured, and how their misconfigurations become test targets. Understand the roles of routers (Layer 3 routing between networks), switches (Layer 2 forwarding, VLANs), firewalls (rule-based filtering, stateful inspection), and proxies/load balancers. Know VLANs as logical segmentation and that VLAN hopping and misconfigured trunk ports are classic weaknesses. Spanning Tree Protocol and loop prevention are relevant to availability questions.
Access control lists on routers and firewall rule ordering matter: rules are evaluated top-down, so a broad permit above a deny can negate the deny. Understand NAT (source and destination) and how it affects what an external tester can see. Know common management interfaces (SSH, HTTPS, SNMP) and that SNMPv1/v2c use community strings sent in clear text - a frequent finding. Default credentials and exposed management planes are recurring themes.
Trap: questions may ask where a control should live (host firewall vs network firewall) or imply that NAT is a security control - it is not, it is address translation that incidentally hides internal addressing.
Rule of thumb: when reviewing a firewall/ACL, read it in order and look for the first matching rule. A permit placed too early is the most common logical flaw.