# TCP Ephemeral port

## Linux 默认 TCP Ephemeral port 范围

```
Linux 2.4 kernel	sysctl net.ipv4.ip_local_port_range	32768 60999
```


## Load balancer 应对 Ephemeral port 用尽的方法

> [https://www.nginx.com/blog/overcoming-ephemeral-port-exhaustion-nginx-plus/](https://www.nginx.com/blog/overcoming-ephemeral-port-exhaustion-nginx-plus/)

 - Enabling Keepalive Connections
 - 同一网口多 ip： [Dynamically Binding Connections to a Defined List of Local IP Addresses](https://www.nginx.com/blog/overcoming-ephemeral-port-exhaustion-nginx-plus/#:~:text=Dynamically%20Binding%20Connections%20to%20a%20Defined%20List%20of%20Local%20IP%C2%A0Addresses)
 - 减少主动关闭后的 TIME_WATIT : `sysctl net.ipv4.tcp_tw_recycle` `sysctl net.ipv4.tcp_tw_reuse` 



## Ref.

```{toctree}
how-to-stop-running-out-of-ephemeral-ports-and-start-to-love-long-lived-connections.md
ephemeral-port-exhaustion-and-how-to-avoid-it.md
```

## Linux Ref.
> - [Bind before connect](https://idea.popcount.org/2014-04-03-bind-before-connect/)
> - [临时端口号(EPHEMERAL PORT)的动态分配](http://linuxperf.com/?p=178)
> - [由 CPU 高负载引发内核探索之旅](https://zhuanlan.zhihu.com/p/587402192)
> - [TCP连接中客户端的端口号是如何确定的？](https://mp.weixin.qq.com/s/C-Eeoeh9GHxugF4J30fz1A)
> - [TCP协议connect的端口选择](https://segmentfault.com/a/1190000041228516)

### WILS: Load Balancing and Ephemeral Port Exhaustion

> [WILS: Load Balancing and Ephemeral Port Exhaustion](https://community.f5.com/t5/technical-articles/wils-load-balancing-and-ephemeral-port-exhaustion/ta-p/287984)



![0151T000003d7vEQAQ.png](ephemeral-port.assets/large.png)