When you configure DNS anycast, multiple DNS name servers share a single IP address. To identify which DNS name server is answering queries, you can configure the hostname and server ID options so the appliance returns the hostname of the DNS name server that is currently answering queries. By default, the hostname and server ID options are disabled on the NIOS appliance. You can configure the hostname bind directive and server-id directive options at the Grid level and override them at the member level. The appliance returns the hostname of the DNS name server that is currently answering queries when a client queries for the hostname.bind or the id.server with record type as TXT and class CHAOS, as follows:
dig @<IP> hostname.bind txt CH dig @<IP> id.server txt CH
To secure the identity of the internet-facing DNS servers, you can configure the hostname and server ID options for
specific Grid members that are internet-facing to return a user defined value instead of the real hostname. Alternatively, you can disable the hostname and server ID options at the Grid level and configure them only for those members that are not internet-facing.
To configure the hostname and server ID options:
- Grid: From the Data Management tab, select the DNS tab, and then select Grid DNS Properties from the Toolbar.
Member: From the Data Management tab, select the DNS tab and click the Members tab -> member checkbox -> Edit icon. - In the Grid DNS Properties or the Member DNS Properties editor, click Toggle Advanced Mode if the editor is in the basic mode.
- Click the Advanced subtab of the General tab and then complete the following:
- Hostname bind directive: Select either Hostname or None from the drop-down list. The default is None. If you select Hostname, the appliance returns the hostname of the DNS name server that is currently answering queries. Selecting None disables the Hostname bind directive option.
In the Member DNS Properties editor, you can also select User defined and specify any hostname of your choice. The appliance returns the specified hostname instead of the real hostname of the DNS name server that is currently answering queries.
Note that you can only use a hostname that contains characters (A-Z or a-z), numbers (0–9), ".", "-", and "_". Additional special characters cannot be used.
To override an inherited setting from the Grid, click Override. To retain the same setting as the Grid, click Inherit. - Server-id directive: Select either Hostname or None from the drop-down list. The default is None. If you select Hostname, the appliance returns the hostname of the DNS name server that is currently answering queries, when a client queries to identify the server ID of the name server that is answering queries.
Selecting None disables the Server-id directive option.
In the Member DNS Properties editor, you can also select User defined and specify a value of your choice. The appliance returns the specified value when a client queries to identify the server ID of the DNS name server that is answering queries.
To override an inherited setting from the Grid, click Override. To retain the same setting as the Grid, click Inherit. - Save the configuration and click Restart if it appears at the top of the screen.