Documentation / 10.8. Frequently Asked Questions
	10.7. NetworkManager and Security		10.9. Troubleshooting

Frequently Asked Questions

In the following, find some frequently asked questions about configuring special network options with NetworkManager.

How to tie a connection to a specific device?

By default, connections in NetworkManager are device type specific: they apply to all physical devices with the same type. If more than one physical device per connection type is available (for example, your machine is equipped with two ethernet cards), you can tie a connection to a certain device by explicitly specifying the hardware address (or MAC address) of the device.

Look up the MAC address of your device either in the Connection Information, available from the applet/widget, or use the output of command line tools like nm-tool or ifconfig. Then start the dialog for configuring network connections from the GNOME Control Center with System+Network Configurations or in KDE 4 from the Personal Settings with Advanced+Network Settings. Choose the connection you want to modify and click Edit. On the Wired or Wireless tab, enter the MAC address of the device and confirm your changes with OK.

How to specify a certain access point in case multiple access points with the same ESSID are detected?

When multiple access points with different wireless bands (a/b/g/n) are available, the access point with the strongest signal is automatically chosen by default. To override this, use the BSSID field when configuring wireless connections.

The Basic Service Set Identifier (BSSID) uniquely identifies each Basic Service Set. In an infrastructure Basic Service Set, the BSSID is the MAC address of the wireless access point. In an independent (ad-hoc) Basic Service Set, the BSSID is a locally administered MAC address generated from a 46-bit random number.

Start the dialog for configuring network connections from the GNOME Control Center with System+Network Configurations or in KDE 4 from the Personal Settings with Advanced+Network Settings. Choose the wireless connection you want to modify and click Edit. On the Wireless tab, enter the BSSID.

How to share network connections to other computers?

The primary device (the device which is connected to the Internet) does not need any special configuration. However, you need to configure the device that is connected to the local hub or machine as follows:

Start the dialog for configuring network connections from the GNOME Control Center with System+Network Configurations or in KDE 4 from the Personal Settings with Advanced+Network Settings. Choose the connection you want to modify and click Edit. Switch to the IPv4 Settings tab. From the Method drop-down list, choose Shared to other computers. That will enable IP traffic forwarding and run a DHCP server on the device. Confirm your changes in NetworkManager.
As the DCHP server uses port 67, make sure that it is not blocked by the firewall: On the machine sharing the connections, start YaST and select Security and Users+Firewall. Switch to the Allowed Services category. If DCHP Server is not already shown as Allowed Service, select DCHP Server from Services to Allow and click Add. Confirm your changes in YaST.

How to provide static DNS information with automatic (DHCP, PPP, VPN) addresses?

In case a DHCP server provides invalid DNS information (and/or routes), you can override it. Start the dialog for configuring network connections from the GNOME Control Center with System+Network Configurations or in KDE 4 from the Personal Settings with Advanced+Network Settings. Choose the connection you want to modify and click Edit. Switch to the IPv4 Settings tab, and from the Method drop-down list, choose Automatic (DHCP) addresses only. Enter the DNS information in the DNS Servers and Search Domains fields. Click Routes to add additional routes ot to override automatic routes. Confirm your changes.

How to make NetworkManager connect to password protected networks before a user logs in?

Define a system connection that can be used for such purposes. For more information, refer to Section 10.7, “NetworkManager and Security”.