网上找了一下资料,发现有网友(没找着那篇文章网址了)讲是因为network 和 hosts文件中的主机名不一样.
查了一下自己的服务器配置,果然两个文件的主机名不一样,hosts中的主机名是默认的.

[root@server ~]# cat /etc/sysconfig/network 
NETWORKING=yes 
NETWORKING_IPV6=no 
HOSTNAME=server

[root@server ~]# cat /etc/hosts 
# Do not remove the following line, or various programs 
# that require network functionality will fail. 
127.0.0.1              localhost.localdomain localhost 
::1             localhost6.localdomain6 localhost6

将hosts文件中的主机名也改成和network中的主机名一样(如下),哇,那速度是相当地快!

[root@server ~]# cat /etc/hosts 
# Do not remove the following line, or various programs 
# that require network functionality will fail. 
#127.0.0.1              localhost.localdomain localhost 
127.0.0.1               server 
::1             localhost6.localdomain6 localhost6