The following documentations are misleading :
https://docs.spring.io/spring-boot/docs/current/reference/html/howto.html#howto.webserver.use-behind-a-proxy-server.tomcat https://docs.spring.io/spring-boot/docs/current/reference/html/application-properties.html#application-properties.server.server.tomcat.remoteip.internal-proxies
To give another configuration for internal-proxies the "//" escape is not needed. Instead of :
server.tomcat.remoteip.internal-proxies=192\\.168\\.\\d{1,3}\\.\\d{1,3} (like in the documentation) the following value should be used :
server.tomcat.remoteip.internal-proxies=192\.168\.\d{1,3}\.\d{1,3}
The same should apply for the application-properties example :
10\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}|192\\.168\\.\\d{1,3}\\.\\d{1,3}|169\\.254\\.\\d{1,3}\\.\\d{1,3}|127\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}|172\\.1[6-9]{1}\\.\\d{1,3}\\.\\d{1,3}|172\\.2[0-9]{1}\\.\\d{1,3}\\.\\d{1,3}|172\\.3[0-1]{1}\\.\\d{1,3}\\.\\d{1,3}|0:0:0:0:0:0:0:1|::1
should be :
10\.\d{1,3}\.\d{1,3}\.\d{1,3}|192\.168\.\d{1,3}\.\d{1,3}|169\.254\.\d{1,3}\.\d{1,3}|127\.\d{1,3}\.\d{1,3}\.\d{1,3}|172\.1[6-9]{1}\.\d{1,3}\.\d{1,3}|172\.2[0-9]{1}\.\d{1,3}\.\d{1,3}|172\.3[0-1]{1}\.\d{1,3}\.\d{1,3}|0:0:0:0:0:0:0:1|::1
This was only tested under the yaml configuration.