FortiGate HA compatibility with PPPoE and DHCP
FortiGate HA is not compatible with PPP protocols such as PPPoE. FortiGate HA is also not compatible with DHCP. If one or more FortiGate unit interfaces is dynamically configured using DHCP or PPPoE you cannot switch to operate in HA mode. Also, you cannot switch to operate in HA mode if one or more FortiGate unit interfaces is configured as a PPTP or L2TP client.
| Configuring an interface for DHCP or PPPoE is only supported in NAT/Route mode. So, usually when configuring HA in Transparent mode an interface being configured for DHCP or PPPoE should not affect HA operation. However, in some cases you may not be able to enable HA if you had configured an interface for DHCP or PPPoE before switching to Transparent mode. So, if you are blocked from operating a Transparent mode FortiGate unit in HA and cannot find another reason for the problem, try switching the FortiGate unit back to NAT/Route mode and setting all interface modes to static before switching to Transparent mode and enabling HA. You could also enable HA before switching to Transparent mode. |
You can configure a cluster to act as a DHCP server or a DHCP relay agent. In both active-passive and active-active clusters DHCP relay sessions are always handled by the primary unit. It is possible that a DHCP relay session could be interrupted by a failover. If this occurs the DHCP relay session is not resumed after the failover and the DHCP client may have to repeat the DHCP request.
When a cluster is operating as a DHCP server the primary unit responds to all DHCP requests and maintains the DHCP server address lease database. The cluster also dynamically synchronizes the DHCP server address lease database to the subordinate units. If a failover occurs, the new primary unit will have an up‑to-date DHCP server address lease database. Synchronizing the DHCP address lease database prevents the new primary unit from responding incorrectly to new DHCP requests after a failover.
Also, it is possible that when FortiGate units first negotiate to form a cluster that a unit that ends up as a subordinate unit in the cluster will have information in its DHCP address lease database that the cluster unit operating as the primary unit does note have. This can happen if a FortiGate unit responds to DHCP requests while operating as a standalone unit and then when the cluster is formed this unit becomes a subordinate unit. Because of this possibility, after a cluster is formed the DHCP address lease databases of all of the cluster units are merged into one database which is then synchronized to all cluster units.