Data Link Layer Advertising with ladvd


Configuring ladvd under pfSense 2.1.5.

ladvd sends LLDP (Link Layer Discovery Protocol) advertisements on all available interfaces. This makes connected hosts visible on managed switches. By default, it will run as a privilege-separated daemon. In addition to LLDP, ladvd also supports the following protocols:

  • Cisco Discovery Protocol (CDP): This is a proprietary Data Link Layer protocol developed by Cisco Systems. It is used to share information about other directly connected Cisco equipment, such as the operating system version and IP address. It can also be used for On-Demand Routing, which is a method of including routing information in CDP announcements so that dynamic routing protocols do not need to be used in simple networks.
  • Extreme Discovery Protocol (EDP): Another proprietary Data Link Layer protocol; this one was developed by Extreme Networks.
  • Nortel Discovery Protocol (NDP): A proprietary Data Link Layer protocol used for discovery of Nortel networking devices and certain products from Avaya and Ciena. The Device and topology information may be graphically displayed network management software. This protocol had its origin in the SynOptics Network Management Protocol (SONMP) in the 1990s. When SynOptics and Wellfleet Communications merged in 1994, the merged company was named Bay Networks, and SONMP was rebranded as the Bay Network Management Protocol (BNMP) or the Bay Discovery Protocol (BDP). When Bay Networks was itself acquired by Nortel, they renamed it the Nortel Discovery Protocol (NDP).

ladvd Installation and Configuration

To install ladvd under pfSense, navigate to System -> Packages. On the list of packages, scroll down to “ladvd”, and press the “plus” button on the right side. When the install page comes up, press the “Confirm” button to confirm installation. The installation should not take more than 5 minutes.

Once ladvd is installed, there will be a new item on the “Services” menu called “LADVD”, from which you can configure ladvd. There are two tabs on the the configuration page, “General” and “Status”. Clicking on the “General” tab will allow you to configure all the basic settings. The “Enable ladvd” check box allows you to enable or disable ladvd. The “Interfaces” list box allows you to select the interfaces to which ladvd will bind (you can select multiple interfaces). The “Auto-enable protocols” check box allows you to auto-enable protocols based on received packets. The “Silent” check box will cause ladvd to function without transmitting packets. The “Management interfaces” dropdown box allows you to select the management interfaces for this host; IPv4 and IPv6 addresses on this interface are auto-detected. In the “System Location” edit box, you can specify the physical location of the host. Finally, the last four check boxes allow you to enable specific Link Layer protocols: currently, LLDP, CDP, EDP and NDP are supported. Pressing the “ladvd” button at the bottom of the page saves the settings.

The second tab, “Status”, allows you to see information about ladvd devices as well as a detailed decode of Link Layer traffic.

External Links:

The official ladvd site

Ubuntu man page for ladvd

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