What Is a Direct Attach Copper (DAC) Cable

Direct Attach Copper (DAC) cables are fixed-length copper twinax cables with connectors at each end that enable direct communication between network devices, typically limited to short distances within a single rack due to signal integrity constraints. As network speeds increase beyond 100GbE, DACs become shorter (generally limited to 5 meters or less) and require thicker shielding, making them less flexible, while longer-distance connectivity increasingly relies on optical communication. Breakout DAC cables allow higher-density connectors like QSFP+ to split into multiple lower-speed connections, though not all network equipment supports this capability.