A system and method for preventing untrusted nodes from sending or receiving management communications. In an environment such as an InfiniBand communication fabric, a management packet (e.g., a packet traversing virtual lane 15) is one of four types: 1) Request from a manager node (e.g., Subnet Manager or SM) to an endnode; 2) Reply from an endnode to a request from the manager; 3) Request from an endnode to the manager; and 4) Reply from the manager to the endnode. Switches (and other routing devices) are configured to allow untrusted nodes to send management packets of types 2 and 3 only, and to receive management packets of types 1 and 4 only. Trusted nodes (e.g., manager nodes, switches) can send and receive all types. Each port of a switch or routing device has an associated indicator reflecting the level of trust afforded the node or switch coupled to the port.