Manuale Utente (Inglese)

DHCP Option 15 (DNS Domain Name) allows DHCP servers to send client hosts a domain name that will be added when the host accesses a resource by name that does not have a domain.

If a host receives an option from a DHCP server that specifies the domain local, then when accessing some resource, for example, server, from the host, the DNS query will automatically go to the address server.local. However, if the request is made to a resource with a domain (for example, www.google.com, where com is the domain), no changes will occur.

This function is configured via the router's command-line interface (CLI) for each DHCP pool. For example, for the main Home segment, the command will look like this:

(config)> ip dhcp pool _WEBADMIN domain local
Dhcp::Pool: Domain option has been saved.
(config)> system configuration save
Core::ConfigurationSaver: Saving configuration...

To remove a domain (in our example, this is local), use the following commands:

(config)> no ip dhcp pool _WEBADMIN domain
(config)> system configuration save

The option can be seen in network packet dumps when receiving an IP address from a DHCP server.

The result of this option is also visible in DNS query dumps when attempting to access a resource by name without a domain.

In practice, this function can be used to work comfortably in networks with a domain structure, where there is a server that stores the DNS records of all network nodes.

Let's consider an example where there is a local network 192.168.222.0/24, which has a Keenetic router 192.168.222.1 and a DNS server 192.168.222.100 (which stores, for example, a record that a particular server has the domain name server.local and the IP address 192.168.222.33).

1. On the Keenetic router, you need to configure the DHCP server option via the CLI as described above.

2. You also need to register the local DNS server for the local domain on the router's Internet Safety page on the DNS Configuration tab; otherwise, requests will go to the provider's DNS servers.

Now, from the host that received an IP address from the Keenetic DHCP server, you can access the server named server.

Similarly, you can simplify access to all hosts on the network (computers, servers, switches, network storage devices, etc.).

Additional information on configuring DHCPOption 2 (Time Offset), 4 (Time Server), 26 (MTU), 42 (NTP Servers), 43 (Vendor Specific Information), 44 (NetBIOS Servers), 60/66 (TFTP Server Name), 67 (Bootfile-Name), 72 (World Wide Web Server ), 121 (Classless Static Routes), 249 (MS Routes) is provided in the article Configuring DHCP options.