The switch is the component most often improvised in a surveillance system, and a frequent source of stutter and dropouts.

1. Add up the access bandwidth: one 2 MP H.265 main stream runs roughly 2 to 4 Mbps, 4 MP about 4 to 6 Mbps, and 8 MP anywhere from 8 to 12 Mbps. Sum them for the total the switch must carry.
2. Check port speed: a 100 Mbps port delivers about 80 Mbps usable. Beyond four 2 MP channels it approaches saturation, showing up as occasional packet loss and corrupted frames. Use all-gigabit switches.
3. Backplane and forwarding rate: switches labelled gigabit but with a limited backplane still congest under concurrent load. Both aggregate port bandwidth and uplink demand must be satisfied.
4. PoE budget: verify total and per-port power, and size the supply at 1.2 times the simultaneous full-load draw to cover night-time IR peaks.
5. Uplink and cascading: beyond 16 channels, use gigabit uplinks and consider aggregation. Cascading several switches easily turns the uplink into the bottleneck.

Recommendation: use all-gigabit PoE switches at the access layer, and design larger projects as a two-tier structure with a core and area access switches. Expansion and fault-finding both get easier.