TechnitiumSoftware/DnsServer · warning · DhcpServerException

No dynamic lease was found for hardware address: {hardwareAd

Error message

No dynamic lease was found for hardware address: {hardwareAddress}

What it means

Thrown by Scope.ConvertToReservedLease(string hardwareAddress) when no DYNAMIC lease matches the hardware address. Only a currently-dynamic lease can be promoted to reserved; reserved or absent leases cause this error.

Source

Thrown at DnsServerCore/Dhcp/Scope.cs:1564

            return removedLease;
        }

        public void ConvertToReservedLease(string hardwareAddress)
        {
            byte[] hardwareAddressBytes = Lease.ParseHardwareAddress(hardwareAddress);

            foreach (KeyValuePair<ClientIdentifierOption, Lease> entry in _leases)
            {
                Lease lease = entry.Value;

                if ((lease.Type == LeaseType.Dynamic) && lease.HardwareAddress.SequenceEqual(hardwareAddressBytes))
                {
                    ConvertToReservedLease(lease);
                    return;
                }
            }

            throw new DhcpServerException("No dynamic lease was found for hardware address: " + hardwareAddress);
        }

        public void ConvertToReservedLease(ClientIdentifierOption clientIdentifier)
        {
            if (!_leases.TryGetValue(clientIdentifier, out Lease lease) || (lease.Type != LeaseType.Dynamic))
                throw new DhcpServerException("No dynamic lease was found for client identifier: " + clientIdentifier.ToString());

            ConvertToReservedLease(lease);
        }

        public void ConvertToDynamicLease(string hardwareAddress)
        {
            byte[] hardwareAddressBytes = Lease.ParseHardwareAddress(hardwareAddress);

            foreach (KeyValuePair<ClientIdentifierOption, Lease> entry in _leases)
            {
                Lease lease = entry.Value;

View on GitHub (pinned to d0484b6c1e)

Solutions

  1. Confirm a dynamic lease exists for the MAC on this scope before promoting.
  2. If the lease is already Reserved, no conversion is needed.
  3. Register a reservation directly instead of converting if no dynamic lease exists.
  4. Verify MAC format matches the stored HardwareAddress.

Example fix

// before
scope.ConvertToReservedLease(mac); // throws if not dynamic

// after
var lease = scope.Leases.FirstOrDefault(l => l.Type == LeaseType.Dynamic && l.HardwareAddress.SequenceEqual(Lease.ParseHardwareAddress(mac)));
if (lease != null) scope.ConvertToReservedLease(mac);
else scope.AddReservedLease(...); // create reservation directly
Defensive patterns

Strategy: validation

Validate before calling

byte[] mac = Lease.ParseHardwareAddress(macString);
bool convertible = scope.Leases.Any(l => l.Type == LeaseType.Dynamic && l.HardwareAddress.SequenceEqual(mac));
if (!convertible) { /* add reservation directly instead */ }

Type guard

static bool HasDynamicLeaseForHardware(Scope scope, string mac){
    var bytes = Lease.ParseHardwareAddress(mac);
    return scope.Leases.Any(l => l.Type == LeaseType.Dynamic && l.HardwareAddress.SequenceEqual(bytes));
}

Try / catch

try { scope.ConvertToReservedLease(macString); }
catch (DhcpServerException ex) when (ex.Message.Contains("No dynamic lease"))
{ /* fall back to creating a reservation explicitly */ }

Prevention

When it happens

Trigger: Calling scope.ConvertToReservedLease(mac) where the matching lease is Reserved (already reserved), Static, or does not exist at all. The loop only converts when lease.Type == LeaseType.Dynamic and the MAC matches.

Common situations: Promoting a client that was never given a dynamic lease, re-promoting an already-reserved lease, or passing a MAC whose stored lease is not Dynamic.

Related errors

AI-assisted analysis of TechnitiumSoftware/DnsServer@d0484b6c1e (2026-08-13). Data as JSON: /api/errors/a89374c2f94f19c6. Report an issue: GitHub.