TechnitiumSoftware/DnsServer · error · ArgumentException

At least one primary name server address must be specified f

Error message

At least one primary name server address must be specified for {} zone.

What it means

Thrown by the SecondaryForwarderZone.PrimaryNameServerAddresses setter when value is null or has zero entries. A secondary conditional forwarder must know where to forward queries, so an empty upstream list is rejected with ArgumentException naming the property.

Source

Thrown at DnsServerCore/Dns/Zones/SecondaryForwarderZone.cs:152

            {
                switch (value)
                {
                    case AuthZoneUpdate.AllowOnlyZoneNameServers:
                    case AuthZoneUpdate.AllowZoneNameServersAndUseSpecifiedNetworkACL:
                        throw new ArgumentException("The Dynamic Updates option is invalid for Secondary Conditional Forwarder zones: " + value.ToString(), nameof(Update));
                }

                base.Update = value;
            }
        }

        public override IReadOnlyList<NameServerAddress> PrimaryNameServerAddresses
        {
            get { return base.PrimaryNameServerAddresses; }
            set
            {
                if ((value is null) || (value.Count == 0))
                    throw new ArgumentException("At least one primary name server address must be specified for " + GetZoneTypeName() + " zone.", nameof(PrimaryNameServerAddresses));

                base.PrimaryNameServerAddresses = value;
            }
        }

        public override bool ValidateZone
        {
            get { return base.ValidateZone; }
            set { throw new InvalidOperationException(); }
        }

        #endregion
    }
}

View on GitHub (pinned to d0484b6c1e)

Solutions

1. Provide at least one NameServerAddress before assigning PrimaryNameServerAddresses.
2. Validate the upstream list is non-empty before constructing/assigning the zone.
3. Treat an empty upstream list as a configuration error at the source (config parser).

Example fix

// before
zone.PrimaryNameServerAddresses = servers; // servers is null/empty

// after
if (servers is null || servers.Count == 0)
    throw new ArgumentException("upstream servers required");
zone.PrimaryNameServerAddresses = servers;

if (value is null || value.Count == 0)
    throw new ArgumentException("At least one upstream name server is required.");
zone.PrimaryNameServerAddresses = value;

static bool HasUpstream(IReadOnlyList<NameServerAddress> v) =>
    v is not null && v.Count > 0;

null

When it happens

Trigger: Setting zone.PrimaryNameServerAddresses = null or an empty list on a SecondaryForwarderZone.

Common situations: Building a forwarder zone from a config where upstream servers are optional and were omitted; clearing servers during reconfiguration before setting new ones; deserialization producing an empty array.

Related errors

• The Query Access option is invalid for Secondary Conditional
• The Dynamic Updates option is invalid for Secondary Conditio
• Network group map contains an invalid network address: {strN
• External to internal translation entries must have same addr
• External to internal translation entries must have same pref

AI-assisted analysis of TechnitiumSoftware/DnsServer@d0484b6c1e (2026-08-13). Data as JSON: /api/errors/12a6fcbdb8f06efd. Report an issue: GitHub.