dns over tcp

About this tag
The tag dns over tcp on WindowsForum.com covers Microsoft's guidance for mitigating DNS cache poisoning attacks by forcing large DNS responses to use TCP instead of UDP. Content discusses setting the MaximumUdpPacketSize registry value to 1221 bytes on Windows DNS servers, including Windows Server 2022, 2025, and Server Core installations. This configuration helps prevent spoofing and cache-poisoning attacks by ensuring responses exceeding the UDP buffer size fall back to TCP. The tag is relevant for Windows administrators and IT professionals managing DNS security and server hardening.

  1. Windows DNS Cache Poisoning Mitigation: Set MaximumUdpPacketSize to 1221 (ADV200013)

    Microsoft has updated guidance in its Security Update Guide advisory ADV200013 — the advisory that covers DNS resolver spoofing and cache‑poisoning attacks — and is explicitly telling administrators that in addition to older server builds the mitigation applies to newer releases such as Windows...
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    • 1221 adv200013 dns dns cache dns forwarders dns over tcp dns registry dns security edns0 firewall dns tcp maximumudppacketsize powershell registry hardening security tips server core tcp dns latency windows server windows server 2022 windows server 2025
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    • Forum: Security Alerts