Red Hat SummitChapter 20. Configuring NetworkManager DHCP settings
NetworkManager provides different configuration options related to DHCP. For example, you can configure NetworkManager to use the build-in DHCP client (default) or an external client, and you can influence DHCP settings of individual profiles.
20.1. Changing the DHCP client of NetworkManager
By default, NetworkManager uses its internal DHCP client. However, if you require a DHCP client with features that the built-in client does not provide, you can alternatively configure NetworkManager to use dhclient.
Note that RHEL does not provide dhcpcd and, therefore, NetworkManager can not use this client.
Procedure
Create the
/etc/NetworkManager/conf.d/dhcp-client.conffile with the following content:[main] dhcp=dhclient
You can set the
dhcpparameter tointernal(default) ordhclient.If you set the
dhcpparameter todhclient, install thedhcp-clientpackage:# dnf install dhcp-clientRestart NetworkManager:
# systemctl restart NetworkManagerNote that the restart temporarily interrupts all network connections.
Verification
Search in the
/var/log/messageslog file for an entry similar to the following:Apr 26 09:54:19 server NetworkManager[27748]: <info> [1650959659.8483] dhcp-init: Using DHCP client 'dhclient'
This log entry confirms that NetworkManager uses
dhclientas DHCP client.
Additional resources
-
NetworkManager.conf(5)man page on your system
20.2. Configuring the DHCP timeout behavior of a NetworkManager connection
A Dynamic Host Configuration Protocol (DHCP) client requests the dynamic IP address and corresponding configuration information from a DHCP server each time a client connects to the network.
When you enable DHCP in a connection profile, NetworkManager waits, by default, 45 seconds for this request to be completed.
Prerequisites
- A connection that uses DHCP is configured on the host.
Procedure
Optional: Set the
ipv4.dhcp-timeoutandipv6.dhcp-timeoutproperties. For example, to set both options to30seconds, enter:# nmcli connection modify <connection_name> ipv4.dhcp-timeout 30 ipv6.dhcp-timeout 30Alternatively, set the parameters to
infinityto configure that NetworkManager does not stop trying to request and renew an IP address until it is successful.Optional: Configure the behavior if NetworkManager does not receive an IPv4 address before the timeout:
# nmcli connection modify <connection_name> ipv4.may-fail <value>If you set the
ipv4.may-failoption to:yes, the status of the connection depends on the IPv6 configuration:- If the IPv6 configuration is enabled and successful, NetworkManager activates the IPv6 connection and no longer tries to activate the IPv4 connection.
- If the IPv6 configuration is disabled or not configured, the connection fails.
no, the connection is deactivated. In this case:-
If the
autoconnectproperty of the connection is enabled, NetworkManager retries to activate the connection as many times as set in theautoconnect-retriesproperty. The default is4. - If the connection still cannot acquire a DHCP address, auto-activation fails. Note that after 5 minutes, the auto-connection process starts again to acquire an IP address from the DHCP server.
-
If the
Optional: Configure the behavior if NetworkManager does not receive an IPv6 address before the timeout:
# nmcli connection modify <connection_name> ipv6.may-fail <value>
Additional resources
-
nm-settings(5)man page on your system
