In today's era, efficient management of network traffic is essential for maintaining smooth and secure operation of IT infrastructure. The iproute2 tool proves to be crucial for advanced routing and management of network traffic on Linux systems, including CentOS 7 distribution. This article provides a detailed guide on configuring and using iproute2 for advanced network traffic routing on CentOS 7.

Prerequisites

• Installed CentOS 7 system
• Terminal access as a root user or via sudo
• Basic knowledge of working in the terminal and networking concepts

Installing iproute2

Iproute2 is typically pre-installed on CentOS 7. However, if it is missing for any reason, you can easily install it using YUM (Yellowdog Updater, Modified):

sudo yum install iproute

Basics of iproute2

The iproute2 tool replaces older sets of networking tools such as net-tools (containing ifconfig, route, netstat, etc.). It enables advanced routing, IP address manipulation, network interface configuration, QoS (Quality of Service) settings, and more.

Configuring Advanced Routing

1. Creating Multiple Routing Tables

For advanced routing, it's often necessary to create multiple routing tables. This allows defining different routing policies for different types of traffic. Configuring multiple routing tables requires modifying the /etc/iproute2/rt_tables file. For example, we can add a table named custom1:

echo "200 custom1" >> /etc/iproute2/rt_tables

2. Defining Rules for Table Usage

After creating a new table, you need to define rules to determine when the table should be used. This is done using the ip rule add command. For instance, to route traffic from a specific IP address using our new table:

ip rule add from 192.168.1.100/32 table custom1

3. Adding Routing Entries to the Table

With rules now set, it's time to add routing entries to the custom1 table. This is done using the ip route add command with the table specification:

ip route add default via 192.168.1.1 dev eth0 table custom1

This command sets the default route for traffic matching the rules to gateway 192.168.1.1 via network interface eth0, but only for entries in the custom1 table.

4. Applying Changes and Testing

After configuring routing tables and rules, it's crucial to apply the changes. In CentOS 7, this usually involves restarting networking services or the entire system. However, for applying routing rules, often re-executing the relevant iproute2 commands is sufficient.

For testing that routing is working as expected, you can use commands like ping or traceroute, specifying the source IP address to match our rules:

ping -I 192.168.1.100 google.com

Advanced routing with iproute2 on CentOS 7 offers a flexible and powerful tool for managing network traffic. With routing tables, routing rules, and careful configuration, it's possible to efficiently control how network traffic is routed within your infrastructure. This approach can improve network performance, security, and overall network management.