环境：阿里云的云服务器（115.29.102.250）-系统centos6.5
maven私服：http://115.29.102.250:8081/nexus/
问题：
1、central远程仓库索引下载不下来。
2、云服务器刚买来的时候远程仓库是可以正常下载的。
3、wget http://repo.maven.apache.org/maven2/.index/nexus-maven-repository-index.properties可以下载
部分log如下：
2016-11-11 20:27:06,442+0800 INFO [pxpool-1-thread-2] *TASK com.sonatype.nexus.plugins.healthcheck.task.HealthCheckTask - Scheduled task (HealthCheckTask) finished :: Health Check Management for Repository central (started 2016-11-11T20:27:01+08:00, runtime 0:00:05.005)
2016-11-11 20:27:06,470+0800 INFO [pxpool-1-thread-2] *TASK org.sonatype.nexus.configuration.application.DefaultNexusConfiguration - Applying Nexus Configuration due to changes in [Scheduled Tasks] made by *TASK...
2016-11-11 20:27:08,470+0800 WARN [pxpool-1-thread-1] admin org.sonatype.nexus.index.DefaultIndexerManager - Cannot fetch remote index for repository "Central" [id=central] due to IO problem.
org.sonatype.nexus.proxy.RemoteStorageException: Transport error while executing GET method [repositoryId="central", requestPath="/.index/nexus-maven-repository-index.properties", remoteUrl="http://repo.maven.apache.org/maven2/.index/nexus-maven-repository-index.properties"]
at org.sonatype.nexus.proxy.storage.remote.httpclient.HttpClientRemoteStorage.doExecuteRequest(HttpClientRemoteStorage.java:616) ~[nexus-core-2.14.1-01.jar:2.14.1-01]
at org.sonatype.nexus.proxy.storage.remote.httpclient.HttpClientRemoteStorage.executeRequest(HttpClientRemoteStorage.java:521) ~[nexus-core-2.14.1-01.jar:2.14.1-01]
at org.sonatype.nexus.proxy.storage.remote.httpclient.HttpClientRemoteStorage.retrieveItem(HttpClientRemoteStorage.java:216) ~[nexus-core-2.14.1-01.jar:2.14.1-01]
at org.sonatype.nexus.index.DefaultIndexerManager$11.retrieve(DefaultIndexerManager.java:1256) ~[nexus-indexer-lucene-plugin-2.14.1-01/:na]
at org.apache.maven.index.updater.DefaultIndexUpdater.downloadIndexProperties(DefaultIndexUpdater.java:465) ~[nexus-indexer-lucene-plugin-2.14.1-01/:na]
log日志可以直接登陆查看，在administration-logging-log。
官方仓库地址：
http://repo1.maven.org/maven2/
http://repo2.maven.org/maven2/
http://repo.maven.apache.org/maven2/
maven私服的密码是原始密码，谁来帮我看下，给提供个解决方案。
