Kerio Tech KERIO WINROUTE FIREWALL 6 - Manual (Page 107)

8.1 DNS module
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Figure 8.2 Editor of the Hosts system file
Local DNS domain
In the When resolving name from the ’hosts’ file or lease table combine it with DNS domain
below entry, specify name of the local DNS domain.
If a host or a network device sends a request for an IP address, it uses the name only (it
has not found out the domain yet). Therefore, only host names without domain are saved
in the table of addresses leased by DHCP server . The DNS module needs to know the
name of the local domain to answer queries on fully qualified local DNS names (names
including the domain).
Note: If the local domain is specified in the DNS module, local names with or without the
domain can be recorded in the hosts system file.
The problem can be better understood through the following example.
Example
The local domain’s name is company.com. The host called john is configured so as to
obtain an IP address from the DHCP server. After the operating system is started the
host sends to the DHCP server a query with the information about its name (john). The
DHCP server assigns the host IP address 192.168.1.56. The DHCP server then keeps the
information that the IP address is assigned to the john host.
Another host that wants to start communication with the host will send a query on the
john.company.com name (the john host in the company.com domain). If the local do-
main name would not have been known by the DNS module, the forwarder would pass the
query to another DNS server as it would not recognize that it is a local host. However, as
DNS Forwarder knows the local domain name, the company.com name will be separated
and the john host with the appropriate IP address will be easily looked up in the DHCP
table.