What causes "Invalid cache maximum entries value. Valid range is 0 and above." in TechnitiumSoftware/DnsServer?

Pass 0 (unlimited) or a positive number for MaximumEntries.

TechnitiumSoftware/DnsServer · error · ArgumentOutOfRangeException

Invalid cache maximum entries value. Valid range is 0 and ab

Error message

Invalid cache maximum entries value. Valid range is 0 and above.

What it means

Thrown by the MaximumEntries property setter when value is less than 0. The cache maximum-entries cap must be zero or positive (0 typically means unlimited/auto), so any negative number is rejected.

Source

Thrown at DnsServerCore/Dns/ZoneManagers/CacheZoneManager.cs:1237

        public uint ServeStaleResetTtl
        {
            get { return _serveStaleResetTtl; }
            set
            {
                if ((value < SERVE_STALE_MIN_RESET_TTL) || (value > SERVE_STALE_MAX_RESET_TTL))
                    throw new ArgumentOutOfRangeException(nameof(ServeStaleResetTtl), "Serve stale reset TTL must be between " + SERVE_STALE_MIN_RESET_TTL + " and " + SERVE_STALE_MAX_RESET_TTL + " seconds. Recommended value is 30 seconds.");

                _serveStaleResetTtl = value;
            }
        }

        public long MaximumEntries
        {
            get { return _maximumEntries; }
            set
            {
                if (value < 0)
                    throw new ArgumentOutOfRangeException(nameof(MaximumEntries), "Invalid cache maximum entries value. Valid range is 0 and above.");

                _maximumEntries = value;
            }
        }

        public long TotalEntries
        { get { return _totalEntries; } }

        #endregion
    }
}

View on GitHub (pinned to d0484b6c1e)

Solutions

Pass 0 (unlimited) or a positive number for MaximumEntries.
Clamp computed values to >= 0 before assigning.
Validate the configured value against the documented range before applying.

Example fix

// before
_cacheZoneManager.MaximumEntries = -1; // < 0 -> throws
// after
_cacheZoneManager.MaximumEntries = 0; // 0 = unlimited, or use a positive cap

Defensive patterns

Strategy: validation

Validate before calling

long max = requestedMaximumEntries < 0 ? 0 : requestedMaximumEntries;
cacheZoneManager.MaximumEntries = max;

Type guard

static bool IsValidMaximumEntries(long v) => v >= 0;

Try / catch

try { cacheZoneManager.MaximumEntries = value; }
catch (ArgumentOutOfRangeException) { cacheZoneManager.MaximumEntries = Math.Max(0, value); }

Prevention

Clamp capacity computations to >= 0.
Use 0 for unlimited when unsure.
Validate config-sourced values before applying.
Guard against arithmetic underflow in size calculations.

When it happens

Trigger: Setting MaximumEntries to a negative number; arithmetic that underflows (e.g. subtracting from a base); config import with a bad value.

Common situations: Script computes capacity from memory/disk and produces a negative; typo/negative literal; stale config value.

Related errors

AI-assisted analysis of TechnitiumSoftware/DnsServer@d0484b6c1e (2026-08-13). Data as JSON: /api/errors/4eb07dff12d00002. Report an issue: GitHub.