Question: What issue might occur when an internal DHCP server is used in a master-master redundancy configuration in the Aruba controller?
Product and Software: This article applies to all Aruba controllers and ArubaOS versions.
When we use an internal DHCP server in master-master redundancy in the Aruba controller, two internal servers must be created (one in master and other in backup-master or standby controller). The chance of IP conflict is always there.
When the master goes down, the standby master takes over. DHCP pools are not synchronized, so two clients may get the same IP address if the same range of address is configured on both of the controllers.
The recommended setting is either to configure the external DHCP server for dynamic IP address assignment or use a different range or scope of IP in the active master and standby master controllers.
Even the internal DHCP server was not intended to serve hundreds of users. Serving DHCP does not introduce a performance impact on the controller, however. The main advantages to using an external server are to avoid duplicate IP addresses and to avoid forcing users to change IP addresses upon failover.
To work around this situation, add scopes on the master and standby that are mutually exclusive.