用netstat命令发现大量的TIME_WAIT现象

 用netstat命令发现大量的TIME_WAIT现象：
netstat -ae|grep 1521|grep root
……
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root
TIME_WAIT   root

检查net.ipv4.tcp_tw当前值，将当前的值更改为1分钟：
[root@aaa1 ~]# sysctl -a|grep net.ipv4.tcp_tw
net.ipv4.tcp_tw_reuse = 0
net.ipv4.tcp_tw_recycle = 0
[root@aaa1 ~]#

vi /etc/sysctl
增加或修改net.ipv4.tcp_tw值：
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_tw_recycle = 1

使内核参数生效：
[root@aaa1 ~]# sysctl -p

[root@aaa1 ~]# sysctl -a|grep net.ipv4.tcp_tw
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_tw_recycle = 1

用netstat再观察正常

这里解决问题的关键是如何能够重复利用time_wait的值，我们可以设置时检查一下time和wait的值
#sysctl -a | grep time | grep wait
net.ipv4.netfilter.ip_conntrack_tcp_timeout_time_wait = 120
net.ipv4.netfilter.ip_conntrack_tcp_timeout_close_wait = 60
net.ipv4.netfilter.ip_conntrack_tcp_timeout_fin_wait = 120