# SDN

Eru 目前的 SDN 其实是独立于 eru-core, 而是让各个 runtime 实现各自的 SDN.

### Docker

Eru 提供了基于 Calico 的 fixed-ip CNM 插件: <https://github.com/projecteru2/barrel/>

它要解决的问题是, 一个容器被 restart (stop && start) 前后的 IP 可能会发生变化, 而对于某些业务来说这是不可接受的风险.

因此使用 eru-barrel CNM 插件之后, 一个 fixed-ip 容器流程是这样的:

1. `docker -H unix:///var/run/barrel.sock run -td --name zc2 --net clouddev --label 'fixed-ip=1' bash bash`: 正常创建容器, 只是多加一个 label `fixed-ip=1`
2. `docker exec -it zc2 ip a sh cali0` 显示容器 IP
3. `docker stop -t0 zc2` 停止容器
4. `calicoctl ipam show --ip` 看到 IP 并没有归还给 calico ippool
5. `docker start zc2` 重启后可以检查 IP 没有改变

Barrel 的配置和安装请参考[文档](https://github.com/projecteru2/barrel/wiki/Install-As-Daemon).

### Yavirt

Yavirt 当前的集成 Calico 方案是基于 tun/tap, 不过在不久的将来会拆解到 CNI.

Yavirt 网络设置请参考[文档](https://github.com/projecteru2/white-paper/blob/master/getstarted/TODO/README.md).


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://book.eru.dev/getstarted/sdn.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.