What is the firewall throughput of the ZyXEL USGFLEX500H?

The firewall throughput is 9.77 Gbit/s.

How many PoE+ ports does the ZyXEL USGFLEX500H have, and what is the power rating of those ports?

It has 2 PoE+ RJ-45 ports, and each port supports 30W.

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ZyXEL High Speed UTM Cyber Security and VPN Firewall, Hardware Only, 2 PoE+ 30W Ports, Nebula Cloud Option, 4 Multi-Gig 2.5G Ports, USGFLEX500H

Gives ultra firewall/UTM/VPN throughput with powerful multi-gig and PoE+ interfaces to get you ready for the multi-gig era
Ultra high performance: Designed with dedicated system resources to minimize packet processing time, reduce latency, and accelerate traffic flows
Port flexibility, Multi-G and PoE+: Features software-defined ports, allowing you true flexibility in tailoring each USG FLEX H port as required (WAN or LAN)
AI-powered cloud cybersecurity: Leverages AI-powered cloud intelligence to operate multi-layered protection such as sandboxing, anti-malware, DNS/IP/URL filtering, IPS, and application patrol over your premises
Hassle free network management with Nebula: Zyxel's centralized cloud management platform you can configure and deploy network and security devices centrally
Preemptive Defense by Reputation Filter: Stop common cyberattacks with Reputation Filter service without sacrificing your network performance thanks to its low computing requirement