DHCP offers a reserved IP

Hello

In our organization we are using 2 DHCP servers for fault tolerance.

Faced with the problem that the one DHCP gives a reserved address on another DHCP.

For example, we have a server 1 and server 2
Server 1 gives addresses from 172.16.4.0 with mask / 23
Exceptions to address 172.16.5.21-254
Server 2 provides the exact same range
In his exclusion range with 172.16.4.21-254 (these addresses issues server 1)

But Server 1 issue address 172.16.5.22 which in reserve on Server 2