Dual-Nic host routing configuration in Linux

Article title: Dual-Nic host routing configuration in Linux. Linux is a technology channel of the IT lab in China. Includes basic categories such as desktop applications, Linux system management, kernel research, embedded systems, and open source.

　　I. environment:

Three directly connected computer hosts

PC1 <------> PC2 <------> PC3

Two NICs eth0 and eth1 are available on PC2, which are connected to PC3 and PC1 respectively.

------ Network cable

　　II. requirements:

Configure PC2 as vro mode to forward packets between PC1 and PC3

　　III. method:

After connecting the three hosts to the Internet using a crossover line as required by the environment, assign network segments for the three hosts and configure IP addresses.

CIDR blocks and IP addresses are allocated as follows:

IP gateway is allocated to the CIDR block of the host name.

PC1: 192.168.2.0/24 192.168.2.2/24 192.168.2.1

PC2: 192.168.2.0/24 192.168.2.1/24 'configuration of the NIC connected to PC1' eth1

192.168.1.0/24 192.168.1.1/24 'configuration of the NIC connected to PC3' eth0

PC3: 192.168.1.0/24 192.168.1.2/24 192.168.1.1

Configure the host IP addresses as shown in the preceding table. Note that to enable PC2 to have the packet forwarding function

Check whether the value in/proc/sys/net/ipv4/ip_forward is 1

Command:

# More/proc/sys/net/ipv4/ip_forward

If the value is not 1 but 0, enter the following command:

# Echo '1'>/proc/sys/net/ipv4/ip_forward

Enable IP forwarding

Other configurations in PC2:

To add a route for PC2, run the following command:

# Route add-net 192.168.1.0 netmask 255.255.255.0 dev eth0

# Route add-net 192.168.2.0 netmask 255.255.255.0 dev eth1

　　IV. verification:

PC1:

Ping Gateway

# Ping 192.168.2.1

# Ping 192.168.1.1

Ping PC3:

# Ping 192.168.1.2

PC3:

Ping Gateway

# Ping 192.168.1.1

# Ping 192.168.2.1

Pint PC1

# Ping 192.168.2.2

　　V. Bug debugging:

The cause of the error mainly lies in PC2.

1. check whether PC2 allows IP packet forwarding (/proc/sys/net/ipv4/ip_forward value is 1)

2. check whether route settings are correct (# press enter to view route information)

This article is from 51CTO. COM Technical Blog