预留端口避免占用ip_local_reserved_ports

预留端口避免占用ip_local_reserved_ports

问题描述：业务遇到这个情况，在重启服务时，出现1986端口被占用而无法启动，非得等该端口释放后才启动成功。

问题分析：1986端口被该服务器上的客户端随机选取源端口给占用掉了。

解决方案：使用net.ipv4.ip_local_port_range参数，规划出一段端口段预留作为服务的端口，这种方法是可以解决当前问题，但是会有个问题，端口使用量减少了，当服务器需要消耗大量的端口号的话，比如反代服务器，就存在瓶颈了。最好的做法是将服务监听的端口以逗号分隔全部添加到ip_local_reserved_ports中，TCP/IP协议栈从ip_local_port_range中随机选取源端口时，会排除ip_local_reserved_ports中定义的端口，因此就不会出现端口被占用了服务无法启动。

Note that ip_local_port_range and ip_local_reserved_portssettings are independent and both are considered by the kernelwhen determining which ports are available for automatic portassignments.

You can reserve ports which are not in the currentip_local_port_range, e.g.:

$ cat /proc/sys/net/ipv4/ip_local_port_range32000 61000$ cat /proc/sys/net/ipv4/ip_local_reserved_ports8080,9148

although this is redundant. However such a setting is usefulif later the port range is changed to a value that willinclude the reserved ports.

[warning]注意：内核版本要大于2.6.18-164，否则不支持该参数。[/warning]