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isc-dhcp-server: Job failed to start – Fix it now

by | Mar 25, 2021

Wondering how to fix ‘isc-dhcp-server: Job failed to start’ error? We can help you fix it.

Here at Bobcares, we have seen several such DHCP-related errors as part of our Server Management Services for web hosts and online service providers.

Today we will see how our Support Engineers fix this DHCP error for our customers.


How we fix ‘isc-dhcp-server: Job failed to start’

Recently, we had a customer who has eth0 and eth1. His eth0 has dynamic IP-address and eth1 has static IP-address. After installing isc-dhcp-server, he went to this one /etc/dhcpd.conf with the following command:

default-lease-time 650;

max-lease-time 79520;

option subnet-mask;
option broadcast-address;
option routers;

subnet netmask




Then he tried to start the server by running the below command.

sudo /etc/init.d/isc-dhcp-server start

As a result, he received the below error message.

start: Job failed to start

Now let’s take a look at the solution our Support Engineers provide to resolve this error.

Here, we found that the customer was using 8 bit subnet mask. So it is not possible to use with 8 bit subnet mask. So we suggested either to change it to or change the mask to

Finally, it must be as below.

subnet netmask

We can also run the DHCP daemon directly to get more information because the startup scripts will eat the error messages.

sudo /usr/sbin/dhcpd -df

This will display the specific complaints it has with the configuration file.

Also, we can see the manual page for the details of -d and -f

man dhcpd

[Need any further assistance in fixing DHCP errors? – We are here to help you]



In short, ‘isc-dhcp-server: Job failed to start’ error can happen if there is any issues with the commands that we run.  Today, we saw the solution provided by our Support Engineers to this DHCP error.


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