TechnitiumSoftware/DnsServer · error · ArgumentOutOfRangeException

Lease time in hours must be between 0 to 23.

Error message

Lease time in hours must be between 0 to 23.

What it means

Thrown by the LeaseTimeHours setter (byte) when the value exceeds 23. Hours are a sub-day component of the lease time and must stay within a 24-hour day (0..23).

Source

Thrown at DnsServerCore/Dhcp/Scope.cs:1898

        public ushort LeaseTimeDays
        {
            get { return _leaseTimeDays; }
            set
            {
                if (value > 999)
                    throw new ArgumentOutOfRangeException(nameof(LeaseTimeDays), "Lease time in days must be between 0 to 999.");

                _leaseTimeDays = value;
            }
        }

        public byte LeaseTimeHours
        {
            get { return _leaseTimeHours; }
            set
            {
                if (value > 23)
                    throw new ArgumentOutOfRangeException(nameof(LeaseTimeHours), "Lease time in hours must be between 0 to 23.");

                _leaseTimeHours = value;
            }
        }

        public byte LeaseTimeMinutes
        {
            get { return _leaseTimeMinutes; }
            set
            {
                if (value > 59)
                    throw new ArgumentOutOfRangeException(nameof(LeaseTimeMinutes), "Lease time in minutes must be between 0 to 59.");

                _leaseTimeMinutes = value;
            }
        }

        public ushort OfferDelayTime

View on GitHub (pinned to d0484b6c1e)

Solutions

1. Clamp to 0..23 before assignment.
2. When converting a total-hour figure, set LeaseTimeDays = total / 24 and LeaseTimeHours = total % 24.
3. Validate config so hours never exceeds 23.
4. Confirm the field is hours, not minutes.

Example fix

// before
scope.LeaseTimeHours = (byte)totalHours; // throws if > 23

// after
scope.LeaseTimeDays  = (ushort)(totalHours / 24);
scope.LeaseTimeHours = (byte)(totalHours % 24);

if (hours > 23) throw new ConfigurationException("LeaseTimeHours must be <= 23");
scope.LeaseTimeHours = (byte)Math.Clamp(hours, 0, 23);

static bool IsValidLeaseTimeHours(int hours) => hours >= 0 && hours <= 23;

try { scope.LeaseTimeHours = value; }
catch (ArgumentOutOfRangeException ex) when (ex.ParamName == "LeaseTimeHours")
{ /* clamp and retry */ }

When it happens

Trigger: Assigning scope.LeaseTimeHours = value where value > 23. Happens when a whole-hour count is split into days/hours incorrectly, or a config feeds a raw hour total into the hours field.

Common situations: Decomposing total hours without dividing by 24, UI not bounding the hours spinner, or deserializing a minutes/hours mix-up.

Related errors

• Lease time in days must be between 0 to 999.
• Lease time in minutes must be between 0 to 59.
• Ending address must be greater than starting address.
• Server host name cannot exceed 63 bytes.
• Boot file name cannot exceed 127 bytes.

AI-assisted analysis of TechnitiumSoftware/DnsServer@d0484b6c1e (2026-08-13). Data as JSON: /api/errors/2d0346fab72a47c2. Report an issue: GitHub.