How HP Web Jetadmin Discovers Network Devices

HP Web Jetadmin uses several methods to find devices connected directly to the network. Regardless of the method used, HP Web Jetadmin first gathers nodes from the network and then determines which of those nodes is a qualified device. Qualification is always done using the SNMP protocol. Nodes found are always queried for specific SNMP objects and then determined to be a qualified printing/imaging device. Once these devices are qualified, HP Web Jetadmin places them in the All Devices list. Each of the methods used to find network devices will be discussed in the following sections.

Maintaining Accurate Address Information

HP Web Jetadmin has the ability to adjust IP addresses stored for each device. In many cases, IP addresses on devices will remain static and changes within the HP Web Jetadmin device lists won’t be needed. In a few cases, device addresses may change due to device moves or when device addresses are assigned with DHCP. In these cases, HP Web Jetadmin should be able to cope with the changes and quickly change its internal record of a device’s IP address.

HP Web Jetadmin will automatically change a devices IP address anytime it has realized a change in that address. For example, a device might have been configured with the IP address 15.62.40.203 yesterday but today it has the IP address 15.62.42.198.

How HP Web Jetadmin Discovers PC-Connected Devices

HP Web Jetadmin can discover printers connected directly to PCs. This discovery facilitates both learning about devices that are connected directly to PC hosts and also gathers detailed information about those devices when the HP SNMP Proxy Agent is being used. The HP SNMP Proxy Agent is a small software package that can be installed onto a PC and facilitates HP Web Jetadmin communications with locally connected devices. PC-Connected discoveries can be performed without the HP SNMP Proxy Agent being installed onto remote hosts but this type of discovery will only gather a minimal amount of device information. This discovery queries desktop and server hosts in order to find locally connected devices. These are devices that are not connected directly to the network, they are connected to the LPT ports or USB ports on the local host.

When one of the types of discoveries for PC-Connected devices is invoked, HP Web Jetadmin communicates directly with the remote host in one of two ways:

●By looking for an HP SNMP Proxy Agent on the local PC if the agent exists, HP Web Jetadmin begins to query the device through the proxy in much the same way as it queries devices directly connected to the network. Through the agent, many pieces of information are available including status, page count, supply levels, and more.

●Through WMI (Windows Management Instrumentation): WMI is a Microsoft service that runs on most Windows operating systems and is used by remote management applications to gather information. HP Web Jetadmin performs a query through WMI on workstations found by way of its various discovery mechanisms. This query attempts to resolve Windows printer model details for devices that are plug and play compatible. The WMI PC-Connected discovery solution does not gather status or other details from the device. The WMI PC-Connected discovery also requires administrator (local) credentials on each host queried.

PC-Connected device discoveries use different query protocols depending on the method used. The table below shows differences in primary and secondary protocols. The primary protocol is used first and if communication is possible through the protocol, devices are queried. The secondary protocol is used when no communication was attained through the primary protocol.

Table 3-4Primary and Secondary Protocols for PC-Connected Device Discoveries

PC-Connected Device Discovery Method

Primary Protocol

Secondary Protocol

 

 

 

IP broadcast

SNMP

WMI*

 

 

 

126 Chapter 3 Device Management

ENWW