Setting the IP address on CentOS¶

In this article

• Centos 7
• Centos 8
• CentOS 9-10 Stream

Centos 7¶

Network interfaces in CentOS 7 are stored and configured through the configuration file /etc/sysconfig/network-scripts/ifcfg-eno1, where eno1 - is the name of the active network card. The names of network card available in the OS, link availability and the current address can be found out by running the command:

ip address

How to configure DHCP¶

Delete the IPADDR, NETMASK, GATEWAY variables, and specify the value dhcp in BOOTPROTO:

NAME="eno1"
ONBOOT=yes
BOOTPROTO=dhcp
HWADDR="ac:1f:6b:f6:3b:7e"
TYPE=Ethernet

How to set up a static IP address¶

The example of configuring a static IP address for an interface named eno1:

```bash
NAME="eno1"
ONBOOT=yes
BOOTPROTO=static
HWADDR="ac:1f:6b:f6:3b:7e"
IPADDR="82.148.21.50"
NETMASK="255.255.255.0"
GATEWAY="82.148.21.1"
TYPE=Ethernet
```

Applying a configuration¶

After changing the configuration file, you need to reload the interface:

systemctl restart network

You can check the network settings using the command:

ip address

NetworkManager¶

Adding an Interface¶

sudo nmcli con add con-name "static-ens224" ifname ens224 type ethernet ip4 192.168.1.76/24 gw4 192.168.1.1

Set up DHCP on the interface:¶

sudo nmcli con mod "System ens192" ipv4.method auto

Set up a static IP address:¶

sudo nmcli con mod "System ens192" ipv4.method manual

After adding routes, you must restart the NetworkManager service.

sudo systemctl restart NetworkManager

Centos 8¶

NetworkManager¶

Adding an Interface¶

$ sudo nmcli con add con-name "static-ens224" ifname ens224 type ethernet ip4 192.168.1.76/24 gw4 192.168.1.1

Set up DHCP on the interface¶

nmcli con add con-name eth3 type ethernet ifname eth3 ipv4.method auto

Set up a static IP address:¶

nmcli con add con-name eth2 type ethernet ifname eth2 ipv4.method manual ipv4.address 192.168.0.15/24 ipv4.gateway 192.168.0.1

After adding routes, you must restart the NetworkManager service.

$ sudo systemctl restart NetworkManager

How to configure DHCP¶

Delete the IPADDR, NETMASK, GATEWAY variables, and specify the value dhcp in BOOTPROTO:

TYPE="Ethernet"
PROXY_METHOD="none"
BROWSER_ONLY="no"
BOOTPROTO="dhcp"
DEFROUTE="yes"
IPV4_FAILURE_FATAL="no"
IPV6INIT="yes"
IPV6_AUTOCONF="yes"
IPV6_DEFROUTE="yes"
IPV6_FAILURE_FATAL="no"
IPV6_ADDR_GEN_MODE="stable-privacy"
NAME="enp1s0"
UUID="d5f41bf4-de0a-43b3-b633-7e2ec6212e58"
DEVICE="enp1s0"
ONBOOT="yes"

How to set up a static IP address¶

The example of configuring a static IP address:

TYPE="Ethernet"
PROXY_METHOD="none"
BROWSER_ONLY="no"
BOOTPROTO="none"
DEFROUTE="yes"
IPV4_FAILURE_FATAL="no"
IPV6INIT="yes"
IPV6_AUTOCONF="yes"
IPV6_DEFROUTE="yes"
IPV6_FAILURE_FATAL="no"
IPV6_ADDR_GEN_MODE="stable-privacy"
NAME="enp1s0"
UUID="d5f41bf4-de0a-43b3-b633-7e2ec6212e58"
DEVICE="enp1s0"
ONBOOT="yes"
IPADDR=192.168.122.66
PREFIX=24
GATEWAY=192.168.122.1
DNS1=192.168.122.1

Applying a configuration¶

After changing the configuration file, you need to reload the interface:

systemctl restart network

You can check the network settings using the command:

ip address

CentOS 9-10 Stream¶

When configuring your network, it's crucial to understand the difference between an active network interface and a connection profile in NetworkManager:

1. Active Network Interface (visible through the ip addr show command) - this is the current working connection, which can be automatically configured via DHCP during system startup.

2. NetworkManager Connection Profile (managed through nmcli connection) - this is a persistent configuration that is saved in the system and applied on each boot.

Before making any configurations, always doing initial check:

• Check active interfaces:

  ip addr show
  

• Check existing NetworkManager profiles:

  nmcli connection show
  

• Check device status:

  nmcli device status
  

If a profile is missing, you need to create it before proceeding with further configuration:

nmcli connection add type ethernet con-name "interface_name" ifname "interface_name" 

1. SSH Connection

Basic connection

ssh username@ip_address

2. Initial Network Diagnostics

• View network interfaces

  ip addr show
  nmcli device status
  

• Check current connections

  nmcli connection show
  

3. Location of Configuration Files

Main directories:

• Connection files: /etc/NetworkManager/system-connections/
• Additional configurations: /etc/NetworkManager/conf.d/
• Main config: /etc/NetworkManager/NetworkManager.conf

How to Configure a Static IP Address¶

Creating a new connection

```bash
nmcli connection add type ethernet con-name "static-eth0" \
ifname eth0 \
ipv4.method manual \
ipv4.addresses 192.168.1.100/24 \
ipv4.gateway 192.168.1.1 \
ipv4.dns "8.8.8.8"
```

Modify an existing one

```bash
nmcli connection modify "System eth0" \
ipv4.method manual \
ipv4.addresses 192.168.1.100/24 \
ipv4.gateway 192.168.1.1 \
ipv4.dns "8.8.8.8"
```

Editing Configuration Files:

• Find the necessary config

  ls /etc/NetworkManager/system-connections/
  

• Open the file for editing

  nano /etc/NetworkManager/system-connections/static-eth0.nmconnection
  

• Set correct access permissions

  sudo chmod 600 /etc/NetworkManager/system-connections/static-eth0.nmconnection
  

Example content of the file for a static IP:

[connection]
id=static-eth0
type=ethernet
interface-name=eth0

[ipv4]
method=manual
addresses=192.168.1.100/24
gateway=192.168.1.1
dns=8.8.8.8

How to Configure the Interface for DHCP¶

nmcli connection modify "System eth0" \
ipv4.method auto

Applying Configuration Changes¶

After modifying the configuration file, you need to reload the interface by following these steps:

1. Reload Configuration:

   systemctl reload NetworkManager
   

2. Restart Connection:

   sudo nmcli connection down "static-eth0"
   sudo nmcli connection up "static-eth0"
   

You can verify network settings using the following commands:

• Check Connection Status:

  nmcli connection show "static-eth0"
  

• Check IP Address:

  ip addr show eth0