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Network routing protocols are divided into two categories: internal gateway protocol and external gateway protocol. Routers use the internal gateway protocol to share information within a single autonomous system. If you are using Linux, you can make it behave like a router through the open source (GPLv2) routing protocol stack Quagga.

What is Quagga?

Quagga is a routing package and is a branch of GNU Zebra. It provides the implementation of all the mainstream routing protocols for Unix-like platforms, such as Open shortest path first (OSPF), routing Information Protocol (RIP), Border Gateway Protocol (BGP) and Intermediate system to Intermediate system Protocol (IS-IS).

Although Quagga implements the routing protocols of IPv4 and IPv6, it is not a complete router. A real router not only implements all routing protocols, but also has the ability to forward network traffic. Quagga only implements the routing protocol stack, while forwarding network traffic is handled by the Linux kernel.

Architecture

Quagga implements different routing protocols through daemons for specific protocols. The daemon name is the same as the routing protocol, with the letter "d" as the suffix. Zebra is the core and protocol-independent daemon that provides an abstraction layer for the kernel and provides Zserv API to Quagga clients through TCP sockets. The daemon for each specific protocol is responsible for running the relevant protocol and establishing a routing table based on the information exchanged.

Quagga architecture

Environment

This tutorial uses the OSPF protocol implemented by Quagga to configure dynamic routing. The environment includes two CentOS 7.7hosts named Alpha and Beta. The two hosts share access to the 192.168.122.0 Universe 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

Install the package

First, install the Quagga package on both hosts. It exists in the CentOS base repository:

Yum install quagga-y

Enable IP forwarding

Next, enable IP forwarding on both hosts, as it will be performed by the Linux kernel:

Sysctl-w net.ipv4.ip_forward = 1

Sysctl-p

Configuration

Now, go to the / etc/quagga directory and create a configuration file for your settings. You need three files:

Configuration file for the zebra.conf:Quagga daemon, where you can define the interface and its IP address and IP forwarding

Ospfd.conf: protocol configuration file in which you can define the network to be provided through the OSPF protocol

Daemons: where you will specify the relevant protocol daemons to run

On the host Alpha

[root@alpha] # cat / etc/quagga/zebra.conf

Interface eth0

Ip address 192.168.122.100/24

Ipv6 nd suppress-ra

Interface eth2

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 eth2

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 the host Beta

[root@beta quagga] # cat zebra.conf

Interface eth0

Ip address 192.168.122.50/24

Ipv6 nd suppress-ra

Interface eth2

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 eth2

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

To use the OSPF protocol, you must allow it to pass through the firewall:

Firewall-cmd-- add-protocol=ospf-permanent

Firewall-cmd-reload

Now, start the zebra and ospfd daemons.

# systemctl start zebra

# systemctl start ospfd

View the routing table on both hosts with the following command:

[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 eth2 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 the routing entries from 192.168.122.50 to 10.10.10.Uniple 24, which are obtained through the protocol zebra. Similarly, on the host Beta, the table contains the route entries that reach network 10.12.13.0 take 24 through 192.168.122.100.

[root@beta ~] # ip route show

Default via 192.168.122.1 dev eth0 proto static metric 100

10.10.10.0/24 dev eth2 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

What is Linux system Linux is a free-to-use and free-spread UNIX-like operating system, is a POSIX-based multi-user, multi-task, multi-threaded and multi-CPU operating system, using Linux can run major Unix tools, applications and network protocols.

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