TechnitiumSoftware/DnsServer · error · ArgumentOutOfRangeException

QPM limit IPv6 prefix valid range is between 0 and 128.

Error message

QPM limit IPv6 prefix valid range is between 0 and 128.

What it means

Thrown by the QpmPrefixLimitsIPv6 property setter when any dictionary key (IPv6 prefix length) is outside 0-128. IPv6 addresses are 128 bits, so prefix lengths beyond that are invalid. Each entry is validated in a loop.

Source

Thrown at DnsServerCore/Dns/DnsServer.cs:7449

        public IReadOnlyDictionary<int, (int, int)> QpmPrefixLimitsIPv6
        {
            get { return _qpmPrefixLimitsIPv6; }
            set
            {
                if (value is null)
                {
                    _qpmPrefixLimitsIPv6 = new Dictionary<int, (int, int)>();
                }
                else if (value.Count > byte.MaxValue)
                {
                    throw new ArgumentOutOfRangeException(nameof(QpmPrefixLimitsIPv6), "QPM Prefix Limits for IPv6 cannot have more than 255 entries.");
                }
                else
                {
                    foreach (KeyValuePair<int, (int, int)> qpmPrefixLimit in value)
                    {
                        if ((qpmPrefixLimit.Key < 0) || (qpmPrefixLimit.Key > 128))
                            throw new ArgumentOutOfRangeException(nameof(QpmPrefixLimitsIPv6), "QPM limit IPv6 prefix valid range is between 0 and 128.");

                        if ((qpmPrefixLimit.Value.Item1 < 0) || (qpmPrefixLimit.Value.Item2 < 0))
                            throw new ArgumentOutOfRangeException(nameof(QpmPrefixLimitsIPv6), "QPM limit value cannot be less than 0.");
                    }

                    _qpmPrefixLimitsIPv6 = value;
                }

                ResetQpsLimitTimer();
            }
        }

        public int QpmLimitSampleMinutes
        {
            get { return _qpmLimitSampleMinutes; }
            set
            {
                if ((value < 1) || (value > 60))

View on GitHub (pinned to d0484b6c1e)

Solutions

1. Ensure all keys are integers in the range 0-128 inclusive.
2. Filter out-of-range keys before assignment.

Example fix

// before
server.QpmPrefixLimitsIPv6 =
    new Dictionary<int,(int,int)> { { 200, (100, 200) } }; // throws

// after
server.QpmPrefixLimitsIPv6 =
    new Dictionary<int,(int,int)> { { 64, (100, 200) } };

foreach (var key in qpmV6.Keys)
    if (key < 0 || key > 128)
        throw new InvalidOperationException($"Invalid IPv6 prefix key: {key}");
server.QpmPrefixLimitsIPv6 = qpmV6;

static bool IsValidV6PrefixKey(int key) => key >= 0 && key <= 128;

try { server.QpmPrefixLimitsIPv6 = qpmV6; }
catch (ArgumentOutOfRangeException) { qpmV6 = qpmV6.Where(kv => kv.Key >= 0 && kv.Key <= 128).ToDictionary(k=>k.Key,v=>v.Value); server.QpmPrefixLimitsIPv6 = qpmV6; }

When it happens

Trigger: Assigning QpmPrefixLimitsIPv6 a dictionary containing a key < 0 or > 128.

Common situations: Passing IPv4-style limits to the IPv6 property by mistake; off-by-one or typo in config; a negative value from a computation.

Related errors

• QPM limit IPv4 prefix valid range is between 0 and 32.
• QPM limit value cannot be less than 0.
• QPM Prefix Limits for IPv6 cannot have more than 255 entries
• QPM Prefix Limits for IPv4 cannot have more than 255 entries
• Valid range is between 1 and 60 minutes.

AI-assisted analysis of TechnitiumSoftware/DnsServer@d0484b6c1e (2026-08-13). Data as JSON: /api/errors/39b3c5d35ed9845a. Report an issue: GitHub.