Setting up a Db2 HADR Pacemaker cluster with Overlay IP as Virtual IP on AWS

Summary

Setting up Virtual IP (VIP) for HADR enabled database provides a common connection point for clients without the need to disclose the actual IP address of the primary and standby server for the database. If a failover occurs, the client can still connect to the new primary by using the VIP, effectively achieving automatic client reroute at the network level. The prerequisite for VIP setup is for the primary and standby servers' IP address to be on the same IP subnet - a requirement that sometimes cannot be easily achieved on cloud servers.

On AWS, Overlay IP address Routing provides the capability to send network traffic to the HADR servers within the AWS VPC by a route table. Effectively, that means one can set up the clients within the same AWS VPC but different availability zones as the Db2 HADR servers and establish connectivity through the Overlay IP address. For clients located in another VPC, or outside the AWS Cloud entirely, additional configuration using AWS Transit Gateways (TGWs) Network Load Balancers, or AWS VPN are required to connect to the Overylay IP.

Similar to standard virtual IP addresses, the Overlay IP address can only be associated with a single HADR database or Mutual Failover instance. In the case of HADR, an optional standby Overlay IP address can also be associated with the standby database to accommodate the HADR reads on standby feature.

Note: For primary and standby VIP configuration in Db2 HADR with Pacemaker on AWS, the Overlay IP solution in this technote must be used instead of the VIP configuration created by using the db2cm tool.