解决Zabbix某台主机突然频繁告警"Zabbix agent on xxxxxx is unreachable for x minutes"

一、某台主机突然某一天频繁告警zabbix agent不可达

查看zabbix agent日志没有发现异常

二、查看zabbix server日志发现这台主机的日志有大量报错信息"first network error"以及"another network error"

[root@zabbix_server etc]# cat /tmp/zabbix_server.log|grep 172.28.5.63|more

 27849:20191218:094413.077 Zabbix agent item "perf_counter[2250]" on host "172.28.5.63" failed: another network error, wait fo
r 15 seconds
 27848:20191218:094428.098 resuming Zabbix agent checks on host "172.28.5.63": connection restored
 27837:20191218:094446.128 Zabbix agent item "net.if.in[Microsoft ISATAP Adapter #2]" on host "172.28.5.63" failed: first networ
k error, wait for 15 seconds
 27849:20191218:094504.088 Zabbix agent item "net.if.out[WAN Miniport (Network Monitor)-QoS Packet Scheduler-0000]" on host "172
.28.5.63" failed: another network error, wait for 15 seconds
 27845:20191218:094519.094 resuming Zabbix agent checks on host "172.28.5.63": connection restored
 27836:20191218:094536.258 Zabbix agent item "net.if.in[Broadcom NetXtreme Gigabit Ethernet #4]" on host "172.28.5.63" failed: f
irst network error, wait for 15 seconds
 27846:20191218:094551.117 resuming Zabbix agent checks on host "172.28.5.63": connection restored
 27843:20191218:094600.102 Zabbix agent item "net.if.out[Broadcom NetXtreme Gigabit Ethernet-WFP LightWeight Filter-0000]" on ho
st "172.28.5.63" failed: first network error, wait for 15 seconds
 27843:20191218:094615.127 resuming Zabbix agent checks on host "172.28.5.63": connection restored
 27837:20191218:094623.818 Zabbix agent item "net.if.in[Broadcom NetXtreme Gigabit Ethernet #4-QoS Packet Scheduler-0000]" on ho
st "172.28.5.63" failed: first network error, wait for 15 seconds
 27847:20191218:094641.112 Zabbix agent item "net.if.in[WAN Miniport (SSTP)]" on host "172.28.5.63" failed: another network erro
r, wait for 15 seconds
 27845:20191218:094657.134 resuming Zabbix agent checks on host "172.28.5.63": connection restored
 27834:20191218:094702.464 Zabbix agent item "vfs.fs.size[D:,free]" on host "172.28.5.63" failed: first network error, wait for 
15 seconds
 27852:20191218:094720.139 resuming Zabbix agent checks on host "172.28.5.63": connection restored
 27840:20191218:094723.709 Zabbix agent item "vm.memory.size[pavailable]" on host "172.28.5.63" failed: first network error, wai
t for 15 seconds
 27847:20191218:094738.149 resuming Zabbix agent checks on host "172.28.5.63": connection restored
 27836:20191218:094802.499 Zabbix agent item "net.if.out[Broadcom NetXtreme Gigabit Ethernet #3]" on host "172.28.5.63" failed: 
first network error, wait for 15 seconds
 27843:20191218:094818.149 resuming Zabbix agent checks on host "172.28.5.63": connection restored
 27832:20191218:094825.129 Zabbix agent item "net.if.in[Broadcom NetXtreme Gigabit Ethernet #3-QoS Packet Scheduler-0000]" on ho
st "172.28.5.63" failed: first network error, wait for 15 seconds
 27851:20191218:094859.175 resuming Zabbix agent checks on host "172.28.5.63": connection restored
 27832:20191218:094903.413 Zabbix agent item "vfs.fs.size[E:,free]" on host "172.28.5.63" failed: first network error, wait for 
15 seconds

三、查看主机TCP连接，发现存在大量的TIME_WAIT连接

四、 百度一下，具体是因为如下原因

从系统启动，Windows Vista 中、 在 Windows 7 中，Windows Server 2008 中和在 Windows Server 2008 R2 中的 497 天后未关闭 TIME_WAIT 状态的所有 TCP/IP 端口

意思是说，系统启动的497天以后，所有在"TIME_WAIT"状态的TCP链接都不会被关闭。TCP端口逐渐被占用完，不能创建新的TCP/IP连接

五、登录主机查看系统运行时长

 正好的前天凌晨出现的频繁告警

六、解决方案

1、重启服务器，但是运行497天后，问题还会出现

2、下载微软补丁

微软官网公告地址

https://support.microsoft.com/zh-cn/help/2553549/all-the-tcp-ip-ports-that-are-in-a-time-wait-status-are-not-closed-aft

现在已经不能下载补丁包了，可以使用window update来更新补丁