BIG-IP system redundancy includes the ability for a device to mirror connection and persistence information to another device, to prevent interruption in service during failover. The BIG-IP system mirrors connection and persistence data over TCP port 1028 with every packet or flow state update.
You enable connection mirroring on a virtual server. This causes an active traffic group within a device service clustering (DSC) configuration to mirror its connections to the designated mirroring peer in the device group. You can enable mirroring for FTP, Telnet, HTTP, and UDP connections.
Connection mirroring operates at the traffic group level. That is, each device in a device group has a specific mirroring peer device for each traffic group. The mirroring peer device is the traffic group's next-active device.
For example, if device Bigip_A is active for traffic group traffic-group-1, and the next-active device for that traffic group is Bigip_C, then the traffic group on the active device mirrors its in-process connections to traffic-group-1 on Bigip_C.
If Bigip_A becomes unavailable and failover occurs, traffic-group-1 on Bigip_C becomes active and continues the processing of any current connections.
You should enable connection mirroring whenever failover would cause a user session to be lost or significantly disrupted. For example, long-term connections such as FTP and Telnet are good candidates for mirroring. For this type of traffic, if failover occurs, an entire session can be lost if the connections are not being mirrored to a peer device.
Conversely, the mirroring of short-term connections such as HTTP and UDP is not recommended, because these protocols allow for failure of individual requests without loss of the entire session, and the mirroring of short-term connections can negatively impact system performance.
Note that connection mirroring only functions between devices that reside on identical hardware platforms. Also note that in addition to enabling connection mirroring on the virtual server, you must also assign the appropriate profiles to the virtual server. For example, if you want the BIG-IP system to mirror FTP connections, you must assign one or more FTP profiles to the virtual server.
Configuring connection mirroring requires you to perform these specific tasks:
You can specify the local self IP address that you want other devices in a device group to use when mirroring their connections to this device. Connection mirroring ensures that in-process connections for an active traffic group are not dropped when failover occurs. You typically perform this task when you initially set up device service clustering (DSC).
You can perform this task to enable TCP or UDP connections for a virtual server. Connection mirroring is an optional feature of the BIG-IP system, designed to ensure that when failover occurs, in-process connections are not dropped. You enable mirroring for each virtual server that is associated with a floating virtual address.
You can perform this task to enable connection mirroring for source network address translation (SNAT). Connection mirroring is an optional feature of the BIG-IP system, designed to ensure that when failover occurs, in-process SNAT connections are not dropped. You can enable mirroring on each SNAT that is associated with a floating virtual address.
You can perform this task to mirror persistence records to another device in a device group.