NetworkManager

Summary

nmcli is a command-line tool used to interact with NetworkManager, a Linux utility that manages network connections. nmcli allows you to create, configure, manage, and troubleshoot network interfaces and connections directly from the terminal without using a graphical interface.

New Network Connection

Gather info

These commands are useful in gathering network information about a host.

ip addr
nmcli con show
nmcli dev status

Delete a connection

nmcli con del {name}

Add a new connection

nmcli con add con-name {name} ifname {interface} type ethernet ipv4.addresses {ip/sm} ipv4.gateway {ip}

Modify existing connection

nmcli con mod {name} ipv4.dns "{ip1},{ip2}"

nmcli con mod {name} ipv4.addr {x.x.x.x/x}

nmcli con mod {name} ipv4.gateway {x.x.x.x}

Bring connection up

nmcli con up {name}

Bring connection down

nmcli con up {name}

Bring connection down/up

Brings it down and then immediately back up, even if you lose connectivity in between (as long as you configured everything correctly).

nmcli con down {name}; nmcli con up {name}

Other Useful Commands

Show all connections

nmcli con show

Show all interfaces

nmcli dev show

nmcli dev status

Add a new connection to an interface

nmcli con add con-name {name} ifname {interface} type ethernet ipv4.addresses {ip/sm} ipv4.gateway {ip} ipv4.dns {ip1},{ip2}

Show details about a connection

nmcli con show {name} | more

Modify the IP address, etc. for an existing connection

nmcli con mod {name} ipv4.addresses {ip/sm}

nmcli con mod {name} ipv4.dns {ip1},{ip2}

nmcli con mod {name} ipv4.dns-search "{domain suffix}"

Create an 802.1Q interface for use on a trunk port

This is also called a VLAN or subinterface.

nmcli con add type vlan con-name {name}.{vlan#} ifname {interface}.{vlan#} dev {interface} id {vlan#} ipv4.addresses {ip/sm} ipv4.gateway {ip}

Bonding

A network bond is a method to combine or aggregate physical and virtual network interfaces to provide a logical interface with higher throughput or redundancy. In a bond, the kernel handles all operations exclusively. You can create bonds on different types of interfaces, such as Ethernet interfaces or VLANs.

Example

In this example, I was able to successfully bond two links to a Juniper EX3300 (and later an EX3400) using LACP (802.3ad):

 Info:  Be sure to delete any existing connection profiles that are applied to any interfaces you plan to use as slaves.

nmcli connection add type bond con-name bond0 ifname bond0 bond.options "mode=802.3ad,lacp_rate=fast"
nmcli connection modify bond0 connection.autoconnect-slaves 1
nmcli connection add type ethernet slave-type bond con-name bond0-port0 ifname enp129s0f0 master bond0
nmcli connection add type ethernet slave-type bond con-name bond0-port1 ifname enp129s0f1 master bond0
nmcli connection modify bond0 ipv4.addresses '10.144.30.20/24' ipv4.gateway '10.144.30.1' ipv4.dns '10.144.30.4,10.150.30.2' ipv4.dns-search 'lambnet.us' ipv4.method manual

Verification

cat /proc/net/bonding/bond0

Also, unplug one member cable of the bond at a time while performing a ping, to confirm link stays up.

Sources

{https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/9/html/configuring_and_managing_networking/configuring-network-bonding_configuring-and-managing-networking https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/9/html/configuring_and_managing_networking/configuring-network-bonding_configuring-and-managing-networking}

{https://www.kernel.org/doc/Documentation/networking/bonding.txt https://www.kernel.org/doc/Documentation/networking/bonding.txt}