Member Avatar for LinuxGuy80

How does VLAN work on Network Manager? I didn't installed the needed packages for network manager through apt-get and or configure the VLAN interface in the command line. The strange problem was that network manager crapped out after deleting the VLAN connection.

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Short answer: NetworkManager on Ubuntu can create and manage 802.1Q VLAN interfaces, but client-side VLAN tagging is normally used on wired links. Wi‑Fi deployments usually map an SSID (or use RADIUS/AAA) to a VLAN on the access point or controller rather than expecting the wireless client to tag frames. (cisco.com)

How this affects your case (): NetworkManager will create persistent VLAN connection profiles and the daemon will bring up a VLAN device when asked. You can create one from the GUI or with nmcli; the command-line form is the same mechanism NetworkManager uses under the hood (so the GUI and nmcli paths are equivalent for persistence). If the kernel module for 802.1Q is missing the VLAN device cannot be created. Example of the nmcli pattern (adjust names/devices for your machine):

sudo nmcli connection add type vlan con-name VLAN100 dev enp0s25 id 100
sudo nmcli connection up VLAN100

See NetworkManager / nmcli docs for exact syntax. (docs.redhat.com)

Why deleting the VLAN could kill Wi‑Fi: removing a VLAN profile can change which interface carries the default route or can leave NetworkManager in a state where the Wi‑Fi connection needs to be reactivated. To recover: restart NetworkManager and check its logs to see why the wireless did not reconnect. On Ubuntu 15.04 you can use systemd/service tools and journalctl, for example:

sudo systemctl restart NetworkManager
journalctl -u NetworkManager --since "10 minutes ago"

(Or: sudo service network-manager restart on systems still using the service wrapper.) (help.ubuntu.com)

Practical checklist and tips (concise):

  • Confirm 8021q module is available before attempting VLANs.
  • List NetworkManager profiles and devices with nmcli connection show / nmcli device status to verify what NM thinks is active.
  • Persistent NM profiles live under /etc/NetworkManager/system-connections (older Ubuntu behavior) — if you have interfaces configured in /etc/network/interfaces, NetworkManager ignores them by default unless you change [ifupdown] managed in NetworkManager.conf. (help.ubuntu.com)

Tiebacks: was correct that Wi‑Fi is usually untagged; if your environment needs VLANs per user or per policy, map them on the AP/RADIUS side rather than relying on client tagging. ’s pointer to VLAN basics is useful background while you apply the steps above.

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Member Avatar for rubberman

This may help: http://www.linuxjournal.com/article/7268

As to why the network manager failed after deleting the VLAN, I can't say, but you may want to check in /etc/sysconfig/network-scripts to see if there are any vlan scripts, and if there are scripts such as ifcfg-eth0 or ifcfg-eth1, etc.

Member Avatar for rubberman

This may help: http://www.linuxjournal.com/article/7268

As to why the network manager failed after deleting the VLAN, I can't say, but you may want to check in /etc/sysconfig/network-scripts to see if there are any vlan scripts, and if there are scripts such as ifcfg-eth0 or ifcfg-eth1, etc. You may want to know that I am basing this from my Red Hat Enterprise Linux 6.x clone. Since you mention apt-get I have to assume you are running a Debian-based system, and there are likely differences between those and RHEL systems.

Member Avatar for LinuxGuy80

I've checked path: /etc/sysconfig/network-scripts which don't exist. The debian based linux distro I'm using is ubuntu and is version 15.04. The question I have is VLAN suppose to work on a wireless network or on a physical ethernet wire? What I meant to say for the OP: The strange bug happened when I deleted the VLAN connection in gnome Network Manager and then resulted with a loss of wireless internet.

Member Avatar for CimmerianX

For Debian based installs (ubuntu) the path rubberman gave you equates to /etc/network/interfaces .
With Network manager, this directory and any interfaces configured within it are ignored. Honestly, I don't understand how network-manager stores all it's data. Manually editing those files are usually going to cause more headaches than anything else. Stick with the net-man gui.

Next, Wifi networks are 99.9% of the time in a native mode, meaning no VLAN tag is applied to the outbound packets. You usually don't need to vlan tag wifi.

I'm wondering what VLAN interface was deleted? "dmesg | grep eth" should give you an idea of what interfaces are available at the moment.

Edited by CimmerianX
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