TechnitiumSoftware/DnsServer · error · InvalidDataException

Lease data format version not supported.

Error message

Lease data format version not supported.

What it means

Deserializing a Lease from its binary stream hit a version byte the reader does not know (the switch default). The supported versions are handled in earlier cases; any other byte is rejected as unsupported.

Source

Thrown at DnsServerCore/Dhcp/Lease.cs:107

                    if (string.IsNullOrWhiteSpace(_hostName))
                        _hostName = null;

                    _hardwareAddress = bR.ReadBuffer();
                    _address = IPAddressExtensions.ReadFrom(bR);

                    if (version >= 2)
                    {
                        _comments = bR.BaseStream.ReadShortString();
                        if (string.IsNullOrWhiteSpace(_comments))
                            _comments = null;
                    }

                    _leaseObtained = bR.BaseStream.ReadDateTime();
                    _leaseExpires = bR.BaseStream.ReadDateTime();
                    break;

                default:
                    throw new InvalidDataException("Lease data format version not supported.");
            }
        }

        #endregion

        #region internal

        internal static byte[] ParseHardwareAddress(string hardwareAddress)
        {
            string[] parts = hardwareAddress.Split(_hyphenColonSeparator);
            byte[] address = new byte[parts.Length];

            for (int i = 0; i < parts.Length; i++)
                address[i] = byte.Parse(parts[i], NumberStyles.HexNumber, CultureInfo.InvariantCulture);

            return address;
        }

View on GitHub (pinned to d0484b6c1e)

Solutions

1. Upgrade the DNS/DHCP server to a version that understands this lease format.
2. Discard/regenerate the affected lease file (leases will be re-acquired by clients).
3. Restore the lease file from a backup written by the same version.

Example fix

// not a code fix: operational
// before: running v6 reading a v8 lease file -> InvalidDataException
// after: upgrade server binary to >= the version that wrote the file, or delete the lease file

// version is inside the binary stream; pre-check by peeking the version byte if you control the file
byte[] header = File.ReadAllBytes(path);
if (header.Length < 2 || header[0] != (byte)'L') throw new InvalidDataException("Not a lease file");
// supported version set must match the running binary

// no static type guard; format version is runtime data

try { var lease = new Lease(reader); }
catch (InvalidDataException ex) when (ex.Message.Contains("version not supported"))
{ /* upgrade server or drop the lease file */ }

When it happens

Trigger: new Lease(BinaryReader) reads a version byte that is not one of the implemented case labels, throwing InvalidDataException from the default branch.

Common situations: Lease file written by a newer server version than the running binary. Corrupted/truncated lease file producing a garbage version byte. Downgrade across a format bump.

Related errors

• Scope data format version not supported.
• DhcpServer scope file format is invalid.
• No lease was found for hardware address: {hardwareAddress}
• No lease was found for client identifier: {clientIdentifier}
• No dynamic lease was found for hardware address: {hardwareAd

AI-assisted analysis of TechnitiumSoftware/DnsServer@d0484b6c1e (2026-08-13). Data as JSON: /api/errors/02dc3968b9719a5a. Report an issue: GitHub.