TranslateProject/sources/tech/20200417 Create a SDN on Linux with open source.md

[#]: collector: (lujun9972)
[#]: translator: (messon007)
[#]: reviewer: ( )
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[#]: subject: (Create a SDN on Linux with open source)
[#]: via: (https://opensource.com/article/20/4/quagga-linux)
[#]: author: (M Umer https://opensource.com/users/noisybotnet)

Create a SDN on Linux with open source 在Linux上使用开源代码创建SDN
======
Make your Linux system act like a router with the open source routing stack Quagga.
使用开源路由协议栈Quagga，使您的Linux系统成为一台路由器。
![Coding on a computer][1]

Network routing protocols fall into two main categories: interior gateway protocols and exterior gateway protocols. Interior gateway protocols are used by routers to share information within a single autonomous system. If you are running Linux, you can make your system behave as a router through the open source (GPLv2) routing stack [Quagga][2].
网络路由协议分为两大类：内部网关协议和外部网关协议。路由器使用内部网关协议在单个自治系统内共享信息。如果您用的是Linux，则可以通过开源（GPLv2）路由协议栈[Quagga][2]使其表现得像一台路由器。

### What is Quagga? 什么是Quagga？

Quagga is a [routing software suite][3] and a fork of [GNU Zebra][4]. It provides implementations of all major routing protocols such as Open Shortest Path First (OSPF), Routing Information Protocol (RIP), Border Gateway Protocol (BGP), and Intermediate System to Intermediate System (IS-IS) for Unix-like platforms.

Although Quagga implements the routing protocols for both IPv4 and IPv6, it doesn't act as a complete router. A true router not only implements all the routing protocols but also has the ability to forward network traffic. Quagga only implements the routing stack, and the job of forwarding network traffic is handled by the Linux kernel.

Quagga是[路由软件包][3]，并且是[GNU Zebra][4]的一个分支。它为类Unix平台提供了所有主流路由协议的实现，例如开放最短路径优先（OSPF），路由信息协议（RIP），边界网关协议（BGP）和中间系统到中间系统协议（IS-IS）。

尽管Quagga为IPv4和IPv6都实现了路由协议，但它却不是一个完整的路由器。真正的路由器不仅实现了所有路由协议，而且还有转发网络流量的能力。 Quagga仅仅实现了路由协议栈，而转发网络流量的工作由Linux内核处理。

### Architecture 架构

Quagga implements the different routing protocols through protocol-specific daemons. The daemon name is the same as the routing protocol followed by the letter "d." Zebra is the core and a protocol-independent daemon that provides an [abstraction layer][5] to the kernel and presents the Zserv API over TCP sockets to Quagga clients. Each protocol-specific daemon is responsible for running the relevant protocol and building the routing table based on the information exchanged.
Quagga通过协议特定的守护程序实现不同的路由协议。守护程序名称与路由协议相同，加了字母“d”作为后缀。Zebra是核心的协议无关的守护进程，它为内核提供了一个[抽象层][5]，并通过TCP套接字向Quagga客户端提供Zserv API。每个协议特定的守护程序负责运行相关的协议并基于交换的信息来建立路由表。

![Quagga architecture][6]

### Setup 环境

This tutorial implements the OSPF protocol to configure dynamic routing using Quagga. The setup includes two CentOS 7.7 hosts, named Alpha and Beta. Both hosts share access to the **192.168.122.0/24** network.

**Host Alpha:**

IP: 192.168.122.100/24
Gateway: 192.168.122.1

**Host Beta:**

IP: 192.168.122.50/24
Gateway: 192.168.122.1

本教程通过Quagga实现的OSPF协议来配置动态路由。该环境包括两个名为Alpha和Beta的CentOS 7.7主机。两台主机共享访问 **192.168.122.0/24** 网络。

**主机Alpha**

IP：192.168.122.100/24
网关：192.168.122.1

**主机Beta**

IP：192.168.122.50/24
网关：192.168.122.1

### Install the package 安装软件包

First, install the Quagga package on both hosts. It is available in the CentOS base repo:
首先，在两台主机上安装Quagga软件包。它存在于CentOS基础仓库中：

```
`yum install quagga -y`
```

### Enable IP forwarding 使能IP转发

Next, enable IP forwarding on both hosts since that will performed by the Linux kernel:
接下来，在两台主机上使能IP转发，因为它将由Linux内核来执行：

```
sysctl -w net.ipv4.ip_forward = 1
sysctl -p
```

### Configuration 配置

Now, go into the **/etc/quagga** directory and create the configuration files for your setup. You need three files:

  * **zebra.conf**: Quagga's daemon configuration file, which is where you'll define the interfaces and their IP addresses and IP forwarding
  * **ospfd.conf**: The protocol configuration file, which is where you'll define the networks that will be offered through the OSPF protocol
  * **daemons**: Where you'll specify the relevant protocol daemons that are required to run



On host Alpha,
现在，进入 **/etc/quagga** 目录并为您的设置创建配置文件。您需要三个文件：

   * **zebra.conf**：Quagga的守护程序配置文件，您可以在其中定义接口及其IP地址和IP转发
   * **ospfd.conf**：协议配置文件，您可以在其中定义将通过OSPF协议提供的网络
   * **守护程序**：您将在其中指定需要运行的相关的协议守护程序


在主机Alpha上，

```
 [root@alpha]# cat /etc/quagga/zebra.conf
interface eth0
 ip address 192.168.122.100/24
 ipv6 nd suppress-ra
interface eth1
 ip address 10.12.13.1/24
 ipv6 nd suppress-ra
interface lo
ip forwarding
line vty

[root@alpha]# cat /etc/quagga/ospfd.conf
interface eth0
interface eth1
interface lo
router ospf
 network 192.168.122.0/24 area 0.0.0.0
 network 10.12.13.0/24 area 0.0.0.0
line vty

[root@alphaa ~]# cat /etc/quagga/daemons
zebra=yes
ospfd=yes
```

On host Beta,
在主机Beta上，

```
[root@beta quagga]# cat zebra.conf
interface eth0
 ip address 192.168.122.50/24
 ipv6 nd suppress-ra
interface eth1
 ip address 10.10.10.1/24
 ipv6 nd suppress-ra
interface lo
ip forwarding
line vty

[root@beta quagga]# cat ospfd.conf
interface eth0
interface eth1
interface lo
router ospf
 network 192.168.122.0/24 area 0.0.0.0
 network 10.10.10.0/24 area 0.0.0.0
line vty

[root@beta ~]# cat /etc/quagga/daemons
zebra=yes
ospfd=yes
```

### Configure the firewall 配置防火墙

To use the OSPF protocol, you must allow it in the firewall:
要使用OSPF协议，必须允许它通过防火墙：

```
firewall-cmd --add-protocol=ospf –permanent

firewall-cmd –reload
```

Now, start the zebra and ospfd daemons.
现在，启动zebra和ospfd守护程序。

```
# systemctl start zebra
# systemctl start ospfd
```

Look at the route table on both hosts using:
用下面命令在两个主机上查看路由表:

```
[root@alpha ~]# ip route show  
default via 192.168.122.1 dev eth0 proto static metric 100
10.10.10.0/24 via 192.168.122.50 dev eth0 proto zebra metric 20
10.12.13.0/24 dev eth1 proto kernel scope link src 10.12.13.1
192.168.122.0/24 dev eth0 proto kernel scope link src 192.168.122.100 metric 100
```

You can see that the routing table on Alpha contains an entry of **10.10.10.0/24** via **192.168.122.50** offered through protocol **zebra**. Similarly, on host Beta, the table contains an entry of network **10.12.13.0/24** via **192.168.122.100**.
您可以看到Alpha上的路由表包含通过 **192.168.122.50** 到达 **10.10.10.0/24** 的条目，它是通过协议 **zebra** 获取的。同样，在主机Beta上，该表包含通过 **192.168.122.100** 到达网络 **10.12.13.0/24** 的条目。

```
[root@beta ~]# ip route show
default via 192.168.122.1 dev eth0 proto static metric 100
10.10.10.0/24 dev eth1 proto kernel scope link src 10.10.10.1
10.12.13.0/24 via 192.168.122.100 dev eth0 proto zebra metric 20
192.168.122.0/24 dev eth0 proto kernel scope link src 192.168.122.50 metric 100
```

### Conclusion 结论

As you can see, the setup and configuration are relatively simple. To add complexity, you can add more network interfaces to the router to provide routing for more networks. You can also implement BGP and RIP protocols using the same method.
如您所见，环境和配置相对简单。要增加复杂性，您可以向路由器添加更多网络接口，以为更多网络提供路由。您也可以使用相同的方法来实现BGP和RIP协议。

--------------------------------------------------------------------------------

via: https://opensource.com/article/20/4/quagga-linux

作者：[M Umer][a]
选题：[lujun9972][b]
译者：[messon007](https://github.com/messon007)
校对：[校对者ID](https://github.com/校对者ID)

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[a]: https://opensource.com/users/noisybotnet
[b]: https://github.com/lujun9972
[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/code_computer_laptop_hack_work.png?itok=aSpcWkcl (Coding on a computer)
[2]: https://www.quagga.net/
[3]: https://en.wikipedia.org/wiki/Quagga_(software)
[4]: https://www.gnu.org/software/zebra/
[5]: https://en.wikipedia.org/wiki/Abstraction_layer
[6]: https://opensource.com/sites/default/files/uploads/quagga_arch.png (Quagga architecture)