com.netflix.discovery.shared.transport.TransportException: Cannot execute request on any known server
	at com.netflix.discovery.shared.transport.decorator.RetryableEurekaHttpClient.execute(RetryableEurekaHttpClient.java:112) ~[eureka-client-1.9.8.jar:1.9.8]
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) ~[eureka-client-1.9.8.jar:1.9.8]
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) ~[eureka-client-1.9.8.jar:1.9.8]
	at com.netflix.discovery.shared.transport.decorator.SessionedEurekaHttpClient.execute(SessionedEurekaHttpClient.java:77) ~[eureka-client-1.9.8.jar:1.9.8]
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) ~[eureka-client-1.9.8.jar:1.9.8]
	at com.netflix.discovery.DiscoveryClient.register(DiscoveryClient.java:829) ~[eureka-client-1.9.8.jar:1.9.8]
	at com.netflix.discovery.InstanceInfoReplicator.run(InstanceInfoReplicator.java:121) ~[eureka-client-1.9.8.jar:1.9.8]
	at com.netflix.discovery.InstanceInfoReplicator$1.run(InstanceInfoReplicator.java:101) [eureka-client-1.9.8.jar:1.9.8]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_201]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_201]
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) [na:1.8.0_201]
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) [na:1.8.0_201]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_201]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_201]
	at java.lang.Thread.run(Thread.java:748) [na:1.8.0_201]

当你配置好你的SpringCloudEureka并加上安全验证时，你发现你客户端连接不上你的服务器时候 ，这时候你就要考虑是不是下面两个问题导致你出现这个错误。

1、Spring Cloud Eureka 客户端配置你的服务注册中心时候 没有加上你服务端安全检查的用户名和密码

spring:
  application:
    name: spring-cloud-eureka-client
  #由于我们前面的eureka的服务端加入spring securit的验证配置 所以这里我们需要加上这个配置信息来能够访问
  security:
    user:
      name: root
      password: root
server:
  port: 8761
eureka:
  client:
    service-url:
      #配置eureka服务注册中心地址 如果eureka server服务注册中心是集群部署 只配置一个其他服务注册中心也能发现
      defaultZone: http://${spring.security.user.name}:${spring.security.user.password}@eureka1:8861/eureka/

@Configuration
@EnableWebSecurity
public class WebSecurityConfig extends WebSecurityConfigurerAdapter {
    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.csrf().disable();
        super.configure(http);
    }
}