Troubleshooting Internal HTTP(S) Load Balancing

This guide describes how to troubleshoot configuration issues for a Google Cloud internal HTTP(S) load balancer. Before following this guide, familiarize yourself with the following:


Load balanced traffic does not have the source address of the original client

This is expected behavior. Internal HTTP(S) Load Balancing positions HTTP(S) proxy servers between clients and backends. When a client program opens a connection to the IP address of an INTERNAL_MANAGED forwarding rule, the connection terminates at a proxy. The proxy processes the requests that arrive over that connection. For each request, the proxy selects a backend to receive the request based on the URL map and other factors. The proxy then sends the request to the selected backend. As a result, from the point of view of the backend, the source of an incoming packet is an IP address from the region's proxy-only subnet.

Requests are rejected by the load balancer

For each request, the proxy selects a backend to receive the request based on a path matcher in the load balancer's URL map. If the URL map doesn't have a path matcher defined for a request, it cannot select a backend service, so it returns an HTTP 404 (Not Found) response code.

Load balancer doesn't connect to backends

The firewalls protecting your backend servers need to be configured to allow ingress traffic from the proxies in the proxy-only subnet range that you allocated to your internal HTTP(S) load balancer's region.

The proxies connect to backends using the connection settings specified by the configuration of your backend service. If these values don't match the configuration of the server(s) running on your backends, the proxy cannot forward requests to the backends.

Clients cannot connect to the load balancer

The proxies listen for connections to the load balancer's IP address and port configured in the forwarding rule (for example,, and with the protocol specified in the forwarding rule (HTTP or HTTPS). If your clients can't connect, ensure that they are using the correct address, port, and protocol.

Ensure that a firewall isn't blocking traffic between your client instances and the load balanced IP address.

Ensure that the clients are in the same region as the load balancer. Internal HTTP(S) Load Balancing is a regional product, so all clients (and backends) must be in the same region as the load balancer resource.


If you are having trouble using Internal HTTP(S) Load Balancing with other Google Cloud networking features, note the current compatibility limitations.