Understand Common DNS RCodes

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Updated:August 29, 2025
Document ID:224714

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    Introduction

    This document describes common Domain Name System (DNS) response codes (RCodes) in DNS query logs.

    Overview

    This table details the function of the most common DNS return messages and corresponding (RCodes) that may appear in your logs while doing a DNS query. Each RCode has its own purpose in the DNS infrastructure. Typically, you see NOERROR (RCODE:0) when doing most of your successful browsing. All of the other return codes are considered errors.

    For an exhaustive list of these codes, please see the DNS RCODEs section of this link: Domain Name System (DNS) Parameters

    DNS Return Message

    DNS Response Code

    Function
    NOERROR RCODE:0

    DNS Query completed successfully
    FORMERR RCODE:1

    DNS Query Format Error
    SERVFAIL RCODE:2

    Server failed to complete the DNS request
    NXDOMAIN RCODE:3

    Domain name does not exist
    NOTIMP RCODE:4

    Function not implemented
    REFUSED RCODE:5

    The server refused to answer for the query
    YXDOMAIN RCODE:6

    Name that can not exist, does exist
    XRRSET RCODE:7

    RRset that can not exist, does exist
    NOTAUTH RCODE:8

    Server not authoritative for the zone
    NOTZONE RCODE:9

    Name not in zone

    Revision History

    Revision Publish Date Comments
    1.0
    29-Aug-2025
    Initial Release
    TAC Authored

    Contributed by Cisco Engineers

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