The Network Inventory provides useful information about the equipment currently installed on your network. In addition to discovering switches and routers when they respond to SNMP queries, Vivinet Assessor uses network device interfaces to determine where your WAN and LAN links are located--important information for troubleshooting future VoIP performance problems caused by link failure or over-subscription.
However, the chief object of the Network Inventory is to populate the Vivinet Assessor database with information about your devices and links, information that is required to perform the Configuration and Utilization assessments.
As a secondary goal, the Network Inventory compiles a list of equipment that will be called upon to handle voice over IP traffic and to identify critical links where that traffic could encounter bottlenecks. If no one has kept careful records each time a new device was added or an operating system upgrade installed, you will now be able to improve your record keeping with the information Vivinet Assessor reports.
Before you start running assessments, you need to know several things about your present or planned VoIP network configuration. First of all, you will save a great deal of time during the Network Inventory if you already know the IP address ranges of the subnets where your network devices are installed. If you try to scan too large a range of subnets, the inventory can take a very long time to complete.
You can change the performance options for the Network Inventory to speed things up. But the faster Vivinet Assessor performs device and link discovery, the more network bandwidth is required. For more information, see Section 3.1.2, Setting Network Discovery Performance.
Do not forget to check the setting for “Max hops” if you decide to perform discovery based on a default gateway router. This setting limits the number of router hops that Vivinet Assessor will query to find network devices and links. For more information, see Section 3.1.3, Using a Default Gateway.
Also, consider the following tips before and after you perform the inventory:
Particularly in the weeks before you roll out a VoIP implementation, you need to know precisely what is installed on your network. For each router and switch, it is helpful to know the manufacturer, in case you need to direct VoIP-specific questions to their support personnel, and the level of the device operating system currently running (it may need to be updated). All this information is collected during the Network Inventory.
It is also important to know exactly where each device is physically located within your campus, building, or site. Such information can be used to construct diagrams of your network’s topology. And those diagrams will be much more helpful to you if you can include the logical identifiers—namely, IP addresses and domain names—of each device, identifiers that are discovered as part of the Inventory.
If some devices in the Inventory show that no information about device location is available, consider configuring a physical location in the MIB for each device. Location is an important means of identification and could end up saving you a lot of time if you ever have to visit a device at its physical home.
Take a close look at the operating system level each device reports. If you are not certain that it is the most recent version of the OS, do some checking at the manufacturer’s Web site and make the recommended updates, if necessary.
Another useful statistic you will find in the Inventory is the Committed Information Rate, or CIR, for discovered frame-relay WAN links. The CIR for your links is an obvious place to begin considering network upgrades if you later find, during the assessment of VoIP Quality, that calls are not performing as well as you would like. The CIR is something you can negotiate with your WAN provider in such a case. Or you can reroute VoIP traffic over faster links.
In results, the Vendor or Operating System information returned may reflect an OEM or pre-acquisition identity for certain devices. For example, some Alcatel devices may show “Xylan” as the Vendor because Xylan was the original developer of the device or its operating system.