X-IPLB-Instance
The HTTP X-IPLB-Instance response header is an unofficial header sent by OVHcloud infrastructure identifying which IP Load Balancing node handled the request.
Note
The "X-" naming convention for HTTP headers, "X" referring to "experimental", has been deprecated and needs to be transitioned to the formal naming convention for HTTP headers.
Usage
OVHcloud's IP Load Balancing (IPLB) service routes traffic across a fleet of load balancer nodes. The X-IPLB-Instance header identifies which specific node in the fleet processed the incoming request before forwarding to the backend.
The value is a numeric instance ID unique to the load balancer within OVH's infrastructure. This node-level detail is useful when debugging routing inconsistencies or performance anomalies tied to a particular path through OVH's network. If two requests to the same origin produce different behavior, comparing X-IPLB-Instance values reveals whether they were handled by different nodes. The header works alongside X-IPLB-Request-Id, which identifies the specific request transaction rather than the node.
Values
Numeric instance identifier
The value is a positive integer identifying the specific IPLB node handling the request. Different values across requests to the same host indicate different load balancer nodes were used.
Example
A response from one OVH load balancer node carries its instance ID in the header.
X-IPLB-Instance: 52345
A different request routed through a different node in the same OVH infrastructure returns a different identifier.
X-IPLB-Instance: 58703
Both IPLB HTTP headers commonly appear together in responses, providing both the node identity and the request identifier.
X-IPLB-Instance: 51946
X-IPLB-Request-Id: 0003B5B7:07BF_0227E461:0050_67C14A5B_3A29E:0836
Takeaway
The X-IPLB-Instance header identifies the OVHcloud load balancer node processing a request. The numeric value enables infrastructure debugging by revealing which node in OVH's IPLB fleet handled each transaction.