Layer 2 Maps

Networks these days are complex and include many cluttered interconnections. Tracking a network's connections and monitoring each of its nodes and links requires technology that's capable of discovering the various layers of that network. The only way to guarantee successful mapping is with a combination of the right mechanisms and a good understanding of how they work. Site24x7's Layer 2 Maps helps network professionals view worthwhile information about the physical interconnections existing in their networks. 

Layer 2—defined as the data link layer—discovers port-to-port connections and linking properties.  

Here is a video to demonstrate network mapping with Site24x7:

The Layer 2 Maps view

Log in to Site24x7, click Network on the left panel, and select Layer 2 Maps. 
Here, you can create and view Layer 2 network maps as well as rediscover, edit, and delete maps.

Figure 1. The Layer 2 Maps view.

Discovery mechanisms

Site24x7 discovers and maps Layer 2 networks based on the following protocols and discovery mechanisms:

• Address Resolution Protocol (ARP): ARP is used to map an IP address to a physical address or media access control address (MAC address) that is recognized on the local device. ARP is mainly for layer 3 switches and routers.
• Cisco Discovery Protocol (CDP): CDP is used to share information about Cisco devices that are directly connected. If your device is a Cisco device, we recommend using CDP for discovery. 
• Forwarding Database (FDB): The FDB table is used by Layer 2 devices to store the MAC addresses that have been discovered and the ports those MAC address were discovered on. In general, switches are discovered using the FDB.
• IP route: IP routes are routes taken from a routing table. Routing tables contain necessary information for forwarding a packet along the best path toward its destination. Common routers and switches are discovered using an IP route.
• Link Layer Discovery Protocol (LLDP): LLDP is used to advertise the identity, capabilities, and neighbors on a wired LAN ethernet. LLDP is used to discover wired LAN ethernets. 

Creating Layer 2 maps

1. Log in to Site24x7.
2. Navigate to Network > Layer 2 Maps > Create New.
3. In the Create Map form that opens, enter the following:
   • Map Name: Enter a name to identify your map.
   • Discover From: Select Devices if you wish to discover and create a network map using a network device that is already being monitored. Select one from the drop-down. If the device is not yet being monitored by Site24x7, choose IP Address and, in the box that appears below, enter the IP address of the device you wish to discover and map. 
   • IP Filters: Enter the start and end IPs of an IP range you want discovered. You should add a minimum of one IP range and can add more by clicking +.
   • Credentials to Use: Choose the credentials to use from the drop-down list. You can choose multiple credentials and add new credentials as well by clicking on + next to the drop-down list.
   • Discovery Mechanisms: Select appropriate discovery mechanisms from the drop-down list. Selecting FDB or LLDP will automatically select ARP along with it. Always select an additional discovery mechanism while choosing ARP. 
   • Location Profile: Choose the On-Premise Poller from which the map has to be discovered (i.e. the On-Premise Poller installed in the same network as the device). 
4. Click Start Discovery.

Figure 2. Discovering a Layer 2 map.

Understanding the discovered Layer 2 maps

• Discovered and monitored devices are displayed as colored tiles for the following statuses: green for Up, red for Down, yellow for Trouble, blue for Configuration error, dark grey for Discovery in progress, lilac for Maintenance, and light grey for Suspended. Unmonitored devices are displayed as white tiles.
• By default, the map structure is displayed as Radial Tree structure, but you can change it to the Node Link structure if you prefer. Once you've changed the structure, don't forget to save your view. 
• You can pan the map, zoom out, or zoom in and, once you've chosen your preferred position, you can save your changes to retain this position.
• Hover over a node to view basic configuration details for the device along with the number of interfaces that are Up, Down, or in Trouble.
• Click on a node to view a graph of the network device's real-time performance stats such as response time and packet loss.
• Hover over links to view basic configuration details, operational states, and admin states of the interface.
• Click on a link to view a graph of the interface's real-time performance stats like traffic, packets, errors, and discards.
• View the status of nodes and links as green, red, or yellow, which denote that they're Up, Down, or in Trouble, respectively.
• View links between network devices turn red or yellow when the connected interface is Down or in Trouble.
• Click Rediscover to obtain the latest status and data of the devices and interfaces.
• You can also edit a map and change IP ranges, credentials, and discovery mechanisms.
• Check the ping response of a device and view its traceroute from the map.

Figure 3. Viewing the Layer 2 map.

Editing the map's layout

Click Edit Layout to edit the map's layout and adjust the spacing between the links. You can edit the layout for both Radial Tree and Node Link structures. Basically, both these structures provide you with the same device interconnection mapping. They only differ in the aesthetic view. The Radial Tree looks like a tree with the seed node at the centre. Whereas, in the Node Link structure, the links are arranged level-wise.

Radial Tree structure:

• Ring Spacing: The spacing between the nodes.

Node link structure:

• Map Orientation: This can either be landscape or portrait. 
• Tree Spacing: The depth of the tree.
• Node Spacing: The spacing between the nodes.
• Sub-tree Spacing: The distance between two sibling nodes.

Adding a discovered device for monitoring

Once your map is discovered, you can add unmonitored devices for monitoring directly from the map. Select the proper credentials, give a proper display name, and start monitoring.

1. Click Add All to add all the discovered, unmonitored devices for monitoring at once. 
2. Hover over an unmonitored device and click Click to monitor to start monitoring that device. 
3. You can also click directly on an unmonitored device to start monitoring it.

Figure 4. Adding a device for monitoring.

Related articles

• Network topology maps
• Visualizing networks
• Switch stack monitoring