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When a device connects to your network and requests an IP address, the expiration 
of the lease will be set to the number of seconds in 
default-lease-time
 if the device 
doesn't explicitly ask for a longer lease time. Here, I'm setting that to 
43200
 seconds, 
which is equivalent to half a day. This basically means that the device will need to 
renew its IP address every 
43200
 seconds, unless it asks for a longer duration.
max-lease-time 86400; 
While the previous setting dictated the default lease time for devices that don't ask 
for a specific lease time, 
max-lease-time
 is the most that the device is allowed to 
have. In this case, I set this to one day (
86400
 seconds). Therefore, no device that 
receives an IP address from this DHCP server is allowed to hold onto their lease for 
longer than this without first renewing it.
option subnet-mask 255.255.255.0; 
With this setting, we're informing clients that their subnet mask should be set to 
255.255.255.0
, which is for a default 24-bit network. If you plan to subnet your 
network, you'll put in a different value here. 
255.255.255.0
 is fine if all you need is 
a 24-bit network.
option broadcast-address 192.168.1.255; 
With this setting, we're telling the client to use 
192.168.1.255
 as the broadcast 
address, which is the last address in the subnet and cannot be assigned to a host.
option domain-name "local.lan"; 
Here, we're setting the domain names of all hosts that connect to the server to 
include 
local.lan
. The domain name is added to the end of the hostname. For 
example, if a workstation with a hostname of 
muffin
 receives an IP address from our 
DHCP server, it will be referred to as 
muffin.local.lan
. Feel free to change this to 
the domain name of your organization, or you can leave it as is if you don't have one.
authoritative;
With the 
authoritative;
 setting (the opposite is 
not authoritative;
), we're 
declaring our DHCP server as authoritative to our network. Unless you are planning 
to have multiple DHCP servers, the 
authoritative;
 option should be included in 
your 
config
 file. We won't use the 
non authoritative;
 option as it's beyond the 
scope of this chapter.

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Setting Up Network Services