Six Numbers to Check Before You Buy a PoE Switch

Two PoE switches can look identical in a quotation and behave completely differently on site. The difference is usually six numbers, most of which sit on page two of the datasheet. This is the checklist we run before quoting, and the one we suggest buyers run before comparing suppliers.

1. Total PoE budget — the number that decides the project

"PoE on 16 ports" says nothing. What matters is the total wattage the power supply can deliver to all ports combined. A 16-port switch with a 120 W budget supports eight 12 W cameras and nothing more, whatever the port count suggests.

• Compare total budget against night draw of every camera, plus 25–30% headroom.
• Check whether the budget is shared across all ports or per port group.
• Ask what happens when demand exceeds the budget — deny new ports, or drop existing ones?

2. Per-port PoE standard and class

af, at and bt are not interchangeable, and a camera declaring class 4 will be refused power on an af port. Mixed fleets are normal, so check that the ports you plan to use support the highest class on site.

3. Switching capacity and packet forwarding rate

These two figures tell you whether the switch can actually move the traffic its ports imply. A unit with gigabit ports but a backplane below the sum of its ports will drop frames under full load — which, on a video network, appears as stutter that no camera setting will fix.

• Switching capacity should be at least 2× total port bandwidth for full duplex.
• Packet forwarding rate should cover the port count at line rate.
• MAC address table size matters on large flat networks; 1K entries is small, 8K+ is comfortable.

4. Uplink type and count

The uplink is what the site will outgrow first. One gigabit uplink on a 24-port PoE switch is fine for video today and a bottleneck when the same cabinet later carries access control and Wi-Fi. Two uplinks allow a ring or a failover pair at almost no extra cost.

If the project needs more, the 2.5G switches and managed 10G models cover the higher tiers; SFP/SFP+ uplinks extend them over fibre.

5. VLANs, IGMP and management depth

If the datasheet lists "web managed" but not VLAN count, IGMP snooping, storm control or per-port PoE on/off, assume none of them. Those four features are what make a switch diagnosable after commissioning, and they are the difference between one vendor's "managed" and another's.

6. Thermal rating, MTBF and warranty

A commercial switch rated 0–40 °C has no place in an outdoor cabinet that reaches 55 °C. Check operating temperature, ventilation requirements, MTBF and the warranty term — and remember that the cheapest unit usually has the shortest warranty and the longest lead time on spares.

Send the camera list and cabinet count and we will return a comparison table with these six numbers filled in for each candidate model. Request a quote.

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