In today’s interconnected world, ensuring high availability of services like DHCP is crucial. ISC-DHCP server, a popular choice for managing network addresses, supports a failover mechanism. This blog post will guide you through the process of checking the synchronization status between primary and secondary servers in a failover configuration.

Setting Up Failover in dhcpd.conf

Before diving into the synchronization status, let’s set up the failover in the dhcpd.conf file. Here, you need to specify the OMAPI port, which is used for management tasks such as checking the failover status. An example configuration is shown below:
omapi-port 7911;

Restart the Service

sudo systemctl restart isc-dhcp-server

Using omshell to Check Failover Status

start the omshell

omshell

and use following commands

server localhost
connect
new failover-state
set name = "internal-network"
open

important note set name , this is your failover name that is defined in the dhcpd.conf
the two important lines from the output above are these

partner-state = 00:00:00:02
local-state = 00:00:00:02

Understanding the Failover Status Output

What is the meaning of this hexadecimal values, if you have other values than 02, than you should check deeper whats wrong.
Indicates the present state of the DHCP server in this failover relationship. Possible values for state are:

1 – startup
2 – normal
3 – communications interrupted
4 – partner down
5 – potential conflict
6 – recover
7 – paused
8 – shutdown
9 – recover done
10 – resolution interrupted
11 – conflict done
254 – recover wait

You can find this in the documentations also
https://kb.isc.org/docs/isc-dhcp-44-manual-pages-dhcpd