Basic Network Configuration
The default network service in Red Hat Enterprise Linux 7 and CentOS 7 is provided by NetworkManager (formerly known as Network), a daemon that dynamically controls and configures the network. It is used to keep current network devices and connections working. It provides tools such as nmCLI (command line tool for configuring the network) that make it easy to manage the network.
The NetworkManager configuration file is stored in /etc/sysconfig/network-scripts/.
Multiple connections can exist for any one device to facilitate switching between devices, but only one connection can be active at any one time.
The device refers to the network interface, and the connection represents the set of Settings that can be configured for the device.
Viewing Network Information
The nmcli dev status command displays the status of all network devices.
The nmcli con show command displays a list of all connections. If only active connections are listed, add the –active option.
Adding a Network Connection
Nmcli con add Is used to add a new network connection.
Control network connection
The nmcli con up command activates the specified connection by specifying the name of the connection instead of the name of the network interface.
The nmcli dev dis command is used to close the connection of the network interface. You can specify the name of the network interface to close the connection.
Modify the connection configuration file
NetworkManager connections have two types of Settings, one is static connection, which is configured by the administrator and stored in the /etc/sysconfig/network-scripts/ifcfg-* configuration file, and the other is active connection data. The data is obtained from the DHCP server and does not persist. To view the information, run the nmcli con show (with connection name) command.
The nmcli con mod command is used to change the connection Settings, and these changes are saved to the corresponding configuration file (/etc/sysconfig/network-scripts/ifcfg-*).
Deleting a Network connection
The nmcli con del command can be used to delete the connection, delete the corresponding configuration file, disconnect the connection from the device, and delete the connection by specifying the name.
Summary of common key NmCLI commands
| The command | use |
|---|---|
| nmcli dev status | The NetworkManager status of all network interfaces is displayed |
| nmcli con show | List all connections |
| nmcli con show name | Lists the current configuration for the connection named Name |
| nmcli con add con-name name | Add a new connection named name |
| nmcli con mod name | Example Modify the configuration of connection name |
| nmcli con reload | The configuration file was reloaded |
| nmcli con up name | Activate the connection named name |
| nmcli dev dis dev | Deactivate dev’s network interface and disconnect the current connection |
| nmcli con del name | Delete the connection and configuration file named name, and disconnect the current connection |
Edit a network configuration file
The configuration modified by using the nmcli con mod command is automatically saved to the corresponding configuration file, but you can also manually modify the configuration file and restart the configuration.
The configuration file is stored in /etc/sysconfig/network-scripts/ and is named ifcfg-name.
Using nmcli versus modifying files directly
| nmcli con mod | Ifcfg – * files | impact |
|---|---|---|
| ipv4.mothod manual | BOOTPROTO=none | IPv4 is configured in static mode |
| ipv4.mothod auto | BOOTPROTO=dhcp | Look for the configuration from the DHCPv4 server. If a static address is also set, the static address will not be activated until the information is obtained from the DHCP server |
| Ipv4. addresses “192.0.0.1/24 192.0.2.254” (Older versions may need to use ipv4.gateway separately) | 24 GATEWAY IPADDR = 192.0.2.1 PREFIX = = 192.0.2.252 | Set the static IPv4 address, network prefix, and default network. If multiple IPv4 addresses are configured, the values end with 1, 2, and 3 in sequence |
| Ipv4. DNS 8.8.8.8 | DNS = 8.8.8.8 | Modifying a DNS Server |
| ipv4.dns-search example.com | DOMAIN=example.com | Set the DOMAIN |
| ipv4.ignore-auto-dns true | PEEERDNS=no | Ignore the DNS server information from the DHCP server |
| ipv6.method manual | IPV6_AUTOCONF=no | The IPv6 address is configured in static mode |
| ipv6.method | IPV6_AUTOCONF=yes | Use SLAAC in router broadcast to configure network Settings |
| ipv6.method dhcp | IPV6_AUTOCONF=no DHCPV6C=YES | Use DHCPv6 instead of SLAAC to configure network Settings |
| ipv6.addresses “2001:db8::a/64 2001:db8::1” | IPV6ADDR=2001:db8::a/64 IPV6_DEFAULTGW=2001:db8::1 | Set the static IPv6 address, network prefix, and default gateway. If multiple IP addresses are set, separate them with Spaces |
| ipv6.dns … | DNS= … | With IPv4 |
| ipv6.dns-serach … | DOMAIN=… | With IPv4 |
| ipv6.ignore-auto-dns true | IPV6_PEERDNS=no | Ignore the DNS information from the DHCP server |
| connection.autoconnect yes | ONBOOT=yes | This connection is automatically activated when the system boots |
| connection.id exx | NAME=exx | The name of this connection |
| connection.interface-name ens3 | DEVICE=ens3 | The connection is bound to a network interface with this name |
| 802-3-ethernet.mac-address … | HWADDR= … | The connection is bound to the network interface that has this MAC address |
