Edge connectivity refers to the manner in which hosts are connected to edge switches. BMC Atrium Discovery version 8.3 introduces Edge Connectivity discovery as a replacement for the network topology feature that was introduced in BMC Atrium Discovery 8.2. It is not a like-for-like replacement, Edge Connectivity does not attempt to calculate overall network topology, rather, it determines which hosts are connected to which edge switches.

Network topology mapping in BMC Atrium Discovery 8.2 required an additional topology run to calculate the topology of a LAN by processing existing Network Devices and calculating switch-to-switch and switch-to-host relationships. Edge connectivity is calculated in the course of a normal discovery run. The separate topology run no longer exists. For information on the previous version of network topology, see the BMC Atrium Discovery version 8.2 documentation.

Edge connectivity discovery occurs when a discovery run takes place. When a switch is discovered, it is queried for port information. The SNMP request (getPortInfo) method gathers information on all ports found on the switch, as well as a list of neighbor MAC addresses found for each port.

When a host is discovered, its MAC address or addresses are determined. Reasoning uses the MAC addresses to determine whether there is a connection between that host and any previously scanned switches, and if so, will create a new one. If a connection already exists, then it is confirmed. If no connection is found, any existing connection is deleted.

• When a host is discovered, an old connection may be deleted, and a connection to a switch may be made or confirmed.
• When a switch is discovered, an old connection may be deleted. No new connections are made.

Connections are only made when a host is discovered Connections are only made when a host is discovered, and when the switch that it is connected to has already been scanned. Both ends of the connection are required before the connection can be confirmed. Consequently, connection information may not be complete until two scans have taken place.

The provenance of a connection is the provenance of the host or the switch, whichever was discovered last.

Enabling or disabling edge connectivity

Edge connectivity is enabled by default in a fresh install of BMC Atrium Discovery version 8.3. See upgrades for information on the behavior of upgraded appliances.

If you do not intend to use the connection information obtained by edge connectivity, you can disable it on the Discovery Configuration page. Disabling edge connectivity will avoid any additional load being put onto switches in your infrastructure. To do this, an additional option Discover neighbor information when scanning network devices is provided in Discovery Configuration. This option controls whether the information on neighboring ports is obtained.

• Select Yes to retrieve neighbor MAC addresses (enable edge connectivity)
• Select No if you do not want to retrieve neighbor MAC addresses (disable edge connectivity)

If you do disable edge connectivity, all existing connections are deleted at the time of the next scan.

Edge connectivity in upgraded appliances

In a fresh install of BMC Atrium Discovery version 8.3, Edge Connectivity discovery is enabled by default. In an upgraded appliance the behavior is as follows:

Where network topology has not been used

Where network topology has not been used, Edge Connectivity discovery is enabled on upgrade. The Topology tab on the Discovery page is removed.

Where network topology has been used

Where network topology has been used, it is retained on upgrade. The Topology tab on the Discovery tab is retained and topology runs can be performed in the same way as BMC Atrium Discovery version 8.2. An information banner is displayed describing the new edge connectivity feature. This is shown in the screen below:

To enable edge connectivity in the upgraded appliance, click the Enable Edge Connectivity Discovery button. The screen is refreshed to show that the network topology has been replaced by edge connectivity. When you do enable edge connectivity on an upgraded appliance you must check to ensure that you have removed any cron jobs that performed scheduled topology runs. See tw_cron_update for details of managing cron jobs.