Linux Networking

Utilities

  • ip

  • ifcfg

  • nmcli

Interfaces

List Ethernet Interfaces on Host

You can use lspci to list PCI-based Ethernet devices on a system.

[root@mawenzi-04 ~]# lspci | grep -i ethernet
c6:00.0 Ethernet controller: Intel Corporation I350 Gigabit Network Connection (rev 01)
c6:00.1 Ethernet controller: Intel Corporation I350 Gigabit Network Connection (rev 01)
c6:00.2 Ethernet controller: Intel Corporation I350 Gigabit Network Connection (rev 01)
c6:00.3 Ethernet controller: Intel Corporation I350 Gigabit Network Connection (rev 01)

Bringing Interfaces Up/Down

Reference

Two methods can be used to bring interfaces up or down.

This does not persist across boots. Once you reboot the node, the link will return to its default state.

Using ip

# ip link set dev <interface> up
# ip link set dev <interface> down

Examples:

ip link set dev eth0 up
ip link set dev eth0 down

Using ifconfig`

# /sbin/ifconfig <interface> up
# /sbin/ifconfig <interface> down

Examples:

/sbin/ifconfig eth0 up
/sbin/ifconfig eth0 down

Hostname

Set hostname using hostnamectl

hostnamectl set-hostname NAME

Set hostname at boot time by editing the grub boot parameters and adding hostname=NAME

Proxies

Set proxy environment for HPE LR1: See Proxies

Firewalls

Disable the firewalld firewall daemon:

systemctl stop firewalld
systemctl disable firewalld

Disable SELinux

setenforce 0

RHEL NetworkManager

The newer style of managing Linux networking, particularly in Rocky Linux 9.X going forward. The older ifconfig network scripts are no longer being used.

In NetworkManager, devices need to be mapped to connections. A connection is a set of configuration options that can be applied to a device. A device can only have one active connection at a time.

NOTE: Network Manager stores its connections in /etc/NetworkManager/system-connections:

[root@mawenzi-06 ~]# ls /etc/NetworkManager/system-connections
ens10f0.nmconnection  ens10f1.nmconnection  ibs1.nmconnection  ibs2.nmconnection

Cracking one of these open we can find critical information about the connection:

Example
[root@mawenzi-06 ~]# cat /etc/NetworkManager/system-connections/ibs1.nmconnection
[connection]
id=ibs1
uuid=bb07b153-64ef-40a9-a703-6beb14b779da
type=infiniband
interface-name=ibs1
timestamp=1702504605

[infiniband]
transport-mode=datagram

[ipv4]
address1=192.168.0.106/24
method=manual

[ipv6]
addr-gen-mode=eui64
method=auto

[proxy]

Network Manager CLI (nmcli)

CLI tool to manage network connections and devices.

Basic Usage

Show active connections
[root@mawenzi-06 ~]# nmcli connection show --active
NAME     UUID                                  TYPE        DEVICE
ens10f0  8a649da4-5810-42a2-b166-2040fddf936c  ethernet    ens10f0
ibs1     bb07b153-64ef-40a9-a703-6beb14b779da  infiniband  ibs1
lo       60cee16c-b863-49a7-a05b-0799d42d0a8f  loopback    lo
Show all connections
[root@mawenzi-06 ~]# nmcli connection show
NAME     UUID                                  TYPE        DEVICE
ens10f0  8a649da4-5810-42a2-b166-2040fddf936c  ethernet    ens10f0
ibs1     bb07b153-64ef-40a9-a703-6beb14b779da  infiniband  ibs1
lo       60cee16c-b863-49a7-a05b-0799d42d0a8f  loopback    lo
ens10f1  31322100-19b2-4893-83a7-c144ad23ec40  ethernet    --
ibs2     95566e3f-d259-40c7-8cec-744694d0ba38  infiniband  --
Show device statuses
[root@mawenzi-06 ~]# nmcli device status
DEVICE   TYPE        STATE                   CONNECTION
ens10f0  ethernet    connected               ens10f0
ibs1     infiniband  connected               ibs1
lo       loopback    connected (externally)  lo
ens10f1  ethernet    unavailable             --
ibs2     infiniband  unavailable             --
Show device configuration (active device)
[root@mawenzi-06 ~]# nmcli device show ibs1
GENERAL.DEVICE:                         ibs1
GENERAL.TYPE:                           infiniband
GENERAL.HWADDR:                         00:00:10:29:FE:80:00:00:00:00:00:00:94:40:C9:FF:FF:B3:3B:60
GENERAL.MTU:                            2044
GENERAL.STATE:                          100 (connected)
GENERAL.CONNECTION:                     ibs1
GENERAL.CON-PATH:                       /org/freedesktop/NetworkManager/ActiveConnection/3
IP4.ADDRESS[1]:                         192.168.0.106/24
IP4.GATEWAY:                            --
IP4.ROUTE[1]:                           dst = 192.168.0.0/24, nh = 0.0.0.0, mt = 150
IP6.ADDRESS[1]:                         fe80::9640:c9ff:ffb3:3b60/64
IP6.GATEWAY:                            --
IP6.ROUTE[1]:                           dst = fe80::/64, nh = ::, mt = 1024
Show device configuration (inactive)
[root@mawenzi-06 ~]# nmcli device show ibs2
GENERAL.DEVICE:                         ibs2
GENERAL.TYPE:                           infiniband
GENERAL.HWADDR:                         00:00:10:29:FE:80:00:00:00:00:00:00:94:40:C9:FF:FF:88:DD:98
GENERAL.MTU:                            4092
GENERAL.STATE:                          20 (unavailable)
GENERAL.CONNECTION:                     --
GENERAL.CON-PATH:                       --
IP4.GATEWAY:                            --
IP6.GATEWAY:                            --

Set Static IP Address

Per the docs:

To set a static IPv4 address, network mask, default gateway, DNS servers, and search domain, enter:

nmcli connection modify ibs1 ipv4.method manual ipv4.addresses 192.168.0.106/24

Set DNS for a Connection

nmcli connection modify ens10f0 ipv4.dns "16.110.135.51 16.110.135.52"

Bring up a Connection

nmcli connection up <connection_name>

Make a Connection Autoconnect

Enabling this will enable the connection upon boot of the system:

nmcli connection modify ibs1 connection.autoconnect yes