@Eric Logsdon Thank you for reaching out to Microsoft Q&A. I understand that you are having questions regarding WAF Front Door functioning as IDS/IPS system.
As you mentioned, IDS/IPS is generally recommended to be at the Perimeter Network i.e. the exit/entry points of Network. Also note that WAFs are designed to protect web applications/servers from web-based attacks (HTTP/HTTPS) whereas IDS/IPS are designed to work on the Network Layer. Therefore, IDS/IPS is provided with the Azure Firewall which works on the Network Layer. Please find more details on deploying IDS/IPS in Azure here. Hope this helps.
Please let us know if you have any further questions and we will be glad to assist you further. Thank you!
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