HP Web Jetadmin IP Range Discovery

Transcription

1 White Paper October 2004 Document Version: 1 Imaging and Printing Group Hewlett-Packard Company Contents 1 Introduction Configuring for Success IP Range Discoveries (Scanning the Network) Developing IP Range Data Other Considerations Impact to the Network Troubleshooting Summary Acronyms Other Resources... 9 HP Web Jetadmin IP Range Discovery Abstract: As print administrators begin using HP Web Jetadmin software, they often ask: - How will I discover every printer or MFP on my network? - Why am I not discovering every printer or MFP on my network? Whether you are attempting to manage devices or extract information about the print environment, you will confront the task of discovering hardcopy devices, possibly all the hardcopy devices on your network. This document discusses a strategic approach to HP Web Jetadmin Discovery. Notice: 2004 Hewlett-Packard Company Microsoft, Windows, and Windows NT are trademarks of Microsoft Corporation in the U.S. and/or other countries. UNIX is a trademark of The Open Group in the U.S. and/or other countries. Intel and Itanium are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the U.S. and other countries. Oracle is a registered U.S. trademark of Oracle Corporation, Redwood City, California. All other product names mentioned herein may be the trademarks of their respective companies. Neither HP, nor any of its subsidiaries, shall be liable for technical or editorial errors or omissions contained herein. The information in this publication is provided "as is" without warranty of any kind and is subject to change without notice. The warranties for HP products are set forth in the express limited warranty statements accompanying such products. Nothing herein should be construed as constituting an additional warranty.

2 1 Introduction HP Web Jetadmin Discovery is the process of searching the network for devices, storing them in a cache, and then displaying the results in a device list. HP Web Jetadmin software contains many different discovery mechanisms, each using a method of either listening to the network or actively generating network signals and waiting for device replies. This document focuses on a superior technique for discovering many network-connected devices but will start with a few factors that may limit device discovery. 2 Configuring for Success Many discovery features exist in HP Web Jetadmin software that can be used to effectively find devices. A few of these features are very good at finding devices on the local IP subnet when HP Web Jetadmin is first installed, but must be configured for discovery on remote networks. When these are configured for remote networks, they may not work as expected due to network infrastructure settings. One example is IP broadcasting which can be blocked at routers in order to reduce large surges or spikes in network traffic. Another is HP Web Jetadmin s ARP Cache discovery which can be very effective at finding printers on the local network during high traffic periods, but can be effectively blocked at the router when SMNP Gets to the router s arp cache are disabled. If these Gets are disabled, HP Web Jetadmin has no way of hopping onto the next network. A few HP Web Jetadmin Discovery mechanisms stand out as superior in finding most if not all network connected printers and MFPs. Specified IP Address discoveries can be extremely effective at discovering devices. This mechanism will query each address (one by one) that the HP Web Jetadmin administrator has provided either through the UI (Figure 1) or through a text file listing device addresses. This address data can be uploaded into the Specified IP Address settings by using the Upload feature in the discovery properties. Again, this mechanism is powerful, but it relies on the fact that the administrator knows all device addresses before HP Web Jetadmin discoveries are deployed. Figure 1 Specified Address Configuration Browse or Upload text file Page 2

3 3 IP Range Discoveries (Scanning the Network) Many times, a ready-made listing of IP addresses may not exist; especially in cases where these questions are being asked: how many devices exist on the network(s), what kind of devices and what are the physical locations? In fact, an initial task may be to gain an understanding or an inventory of all network connected hardcopy devices. IP Range discovery can provide a scanning action of entire networks if configured properly. The remainder of this document focuses on the idea of configuring IP ranges and IP range sets to be scanned for the purpose of discovering all devices in the network environment. IP Range Discovery sends a specific SNMP query to each address as defined in a range or multiple ranges. In a multiple range configuration, each IP range consists of two addresses: a start and an end. These addresses form the basis for address lists. IP Range Discovery is configured within the HP Web Jetadmin properties page (Figure 2). Ranges can be or added to discovery settings through the UI or they can be uploaded from a text file by using the Import Range List feature. This feature is valuable when large numbers of ranges are required. Import Range List Figure 2 IP Range Configuration in HP Web Jetadmin The main task in configuring IP range discoveries is developing range data. Administrators should consider the following questions when developing IP ranges: Which parts of the network should be scanned? Should the entire network be scanned and how long will that take? What IP segments represent IP ranges for the network? Does scanning just one range make sense? Is the network segmented so that large contiguous segments of unused addresses exist? The last two questions are important when formulating IP ranges for HP Web Jetadmin Discovery. Consider the way in which packets are presented to the network during IP Range discovery. IP Range discovery works by sending bursts of SNMP queries onto the network and then waiting a specific period of time for responses. Once the time period is complete, the discovery moves Page 3

4 onto the next burst or set of addresses to query. There are timeouts between each SNMP query as well. These timeouts provide a means of controlling accuracy and also speed. 4 Developing IP Range Data Why is it important to know all of this? IP Range discoveries, while powerful, can also be problematic if configured improperly. Timeouts, while important to accuracy, can cause IP Range discovery to be painfully slow if a large quantity of IP addresses are being scanned that don t represent active network devices. The key to configuring effective and fast IP Range discoveries is in having IP ranges represent only the active portions of the network. Here is a look at two very different IP Range configuration example-scenarios. Scenario 1 (scanning large ranges) With the HP/Compaq networks combined, two ranges can be formed for HP Web Jetadmin discoveries. These two ranges are Although these ranges would work, HP Web Jetadmin would run for an extremely long time before finishing the discovery. Large portions of these two networks are unused and would cause HP Web Jetadmin to spend a great deal of time waiting for responses from devices that don t exist. A better method would be to create many ranges that represent portions of the network that are being used. Note: These addresses are being used for illustrative purposes and don t reflect actual network addressing at HP facilities. Scenario 2 (scanning portions of the network) An administrator tasked with formulating these ranges should have a conversation with the Networking or IT departments to learn which portions of the IP network are active and where each segment is located geographically. Once these facts about the network are known lists of ranges contained within text files can be developed. A plan to run several discoveries over a one week time period can also be devised based upon geographic locations of IP segments/ranges. Here are some brief examples of the files that can be created: File: region1.txt (to be run at 9:00 AM local time) Page 4

5 File: region2.txt (to be run at 9:00 AM local time) File: region3.txt (to be run at 6:00 PM local time) File: region4.txt (to be run at 6:00 PM local time) File: region5.txt (to be run at 2:00 AM local time) File: region6.txt (to be run at 2:00 AM local time) Again, communication with IT or network administration is recommended in order to develop correct IP Range information. On a large network, such as in the example, it is easy to derive literally hundreds of IP Ranges and then map the active IP segments into an IP Range discovery. IT or Networking administration may even provide the details of IP networking in a spreadsheet making it easy to break up ranges and create text files for quick uploading. Most IP networks are not as big as the one described in this example. An important thing to remember is: each network is unique and is made up of one or more contiguous segments of active IP addresses. Once known, these segments can easily be translated into IP Ranges and can be used to perform effective HP Web Jetadmin discoveries. 5 Other Considerations In the second example, files were created that had multiple IP ranges representing active IP addresses in geographic regions. The IP range data from these files can be uploaded in the IP Range discovery settings by using the Import Range List feature. Notice that a schedule remark is placed in the example that denotes the time that a discovery will run. One thing to take into consideration during discovery planning is the fact that many of IP segments reside in regions outside of the HP Web Jetadmin host s home area. This means that when some people are at Page 5

6 work, many other people in other regions are not and devices may have been powered off. In the example, the decision is apparent that discoveries are run at the regional time which will allow maximum accuracy. Administrators should run the discovery whenever devices are powered on. HP introduced a new Discovery, schedule feature in version 7.8 that enables administrators to create unique and individual discovery profiles. Each discovery profile can be implemented with different settings and also be scheduled to launch at a predefined time. This is a great addition to the HP Web Admin discovery feature set in that it will enable administrators to specify different IP range sets to be scanned on individualized schedules. An example would be an administrator who resides in Korea but wants to understand what devices reside on subnets in Europe and North America as well as in Korea. Now the administrator can set up the discovery so that each set of multiple ranges can be scanned during the appropriate time for the region. With this new feature, range-switching is no longer needed all the administrator has to do is specify the correct range sets when scheduling HP Web Jetadmin discoveries. The new Discovery schedule feature is show below in Figure 3. Figure 3 HP Web Jetadmin Discovery Properties Discovery properties can be adjusted for individual, pre-existing schedules or new schedules can be created using Scheduled Discovery Properties. In either case, the software will use range set data that was added to Discovery properties within the IP Range Discovery settings. Another useful feature that was added to HP Web Jetadmin 7.8 is IP Range tagging which enables the administrator to add a descriptive tag to each range as it is entered through IP Range settings or through a file upload. Figure 4 shows the file format for uploading ranges with tags. Page 6

7 Figure 4 - Descriptive IP Range Tag Upload Using IP Range tags, an administrator can label individual subnets to denote physical location, organization or other attributes. In this way, both the source file and the HP Web Jetadmin interface can be used to quickly determine information related to the IP address structure being scanned. Another common network scenario is where specified IP scoping is created to accommodate printer addressing (common in DHCP environments.) In these cases, small numbers of IP addresses on each segment are reserved for printing and can facilitate an easy way to develop IP range data. An example of this would be a small range like 15.X.X X.X.25 that is set aside for hardcopy devices. Assuming a subnet mask of , 15 possible printdevice addresses exist on each segment. Again, this is an easy way to formulate IP ranges and also a common practice in many IP environments. 6 Impact to the Network In most cases, network administrators are concerned with network bandwidth and will put focus on applications like HP Web Jetadmin that use active means to discover network devices. Web Jetadmin s footprint on modern networks is compact and is typically not an issue. Here are some details of an IP range discovery: 300 bytes per each IP query packet (UDP) that occur roughly every 100mSec. Any hardcopy device that responds to this query generates a packet containing about 1100 bytes. Again, the query packets are generated in bursts of 30 and have about a 1- second delay between each burst. During IP Range discovery, initial SNMP Get packets are directed at each IP address as designated by user configured IP range data. Each of these packets contains 13 SNMP objects spanning the standard host resource MIB and a proprietary HP Jetdirect MIB. Networked devices, not limited to printers and that have SNMP agent, will respond to a number these objects based on the manufacturer implementation of SNMP. HP has performed limited testing in customer environments that constitute typical networking. In these tests, it was found that HP Web Jetadmin discoveries do not utilize unacceptable levels of network bandwidth either on the local subnet or on network links. Page 7

8 7 Troubleshooting Problems discovering devices can be encountered in a few cases. Either a single device is known to exist on a network and Web Jetadmin fails to display it, or a network with many devices exists and Web Jetadmin fails to display any of them. Troubleshooting these cases is fairly easy. Here are a few scenarios and some steps that can be taken. After performing an IP Range discovery on a remote network, one device on that network is not appearing in HP Web Jetadmin. To troubleshoot this problem, follow these steps: 1. With the IP address known, Ping can be used to determine if the IP address is reachable. Note, in rare cases ICMP echo requests may be blocked at the router, Ping may not be a good troubleshooting tool in this case. 2. Once the address is established as being active, a browser can be used to access the device s web server in order to verify that the device is a printer or MFP. 3. HP Web Jetadmin s Quick Device Find (Figure 5) is a great test to direct an SNMP query at the device. This step is important. If HP Web Jetadmin can find the device through Quick Device Find, then you know that SNMP communication can occur between the device and the application. Figure 5 Quick Device Find There are a few reasons that SNMP communication can fail to take place between HP Web Jetadmin and a device: 1. SNMP (port 161) is not enabled on the router or gateway to that remote network. IT or network administration should be consulted to determine if SNMP communication is possible on a remote IP subnet 2. SNMP has been disabled on the device. In HP Jetdirect print servers it is possible to disable SNMP. For more information on how to adjust SNMP settings, see documentation regarding the HP Jetdirect EWS interface. 3. HP Web Jetadmin SNMP timeouts are set too low. Perhaps the remote network has a slow link. Use HP Web Jetadmin Device Management, Management, Network Settings to adjust SNMP timeout and retry values. Also, determine if only one device is failing to appear in HP Web Jetadmin for a given subnet. If no devices are discovered, this may indicate blocked SNMP or delay problems. If only one device is un-discovered then the focus of troubleshooting should be on that device. Page 8

9 In cases where only some of the devices are found on a remote network adjustments can be made. IP Range discovery settings can be found in the HP Web Jetadmin application directory in the file %WJADIR%\hpenum.ini. These settings control two items, range burst size and range burst timeout. Try decreasing the range burst size and increasing the range burst timeout when scanning networks that are connected through slow links. Here is the section of the hpenum.ini that contains these settings: 8 Summary [settings] RangeBurstCount=30 RangeBurstTimeout=1000 RangeNodeTimeout=100 RangeRepeatCount=1 Here is a review of IP Range discovery items discussed in this document. First, this discovery mechanism is versatile in that it can scan all IP networks by directing query packets at each IP address represented by an IP range. IP Range discoveries require the administrator to formulate and enter ranges based on the network(s) to be scanned. IP Range discoveries can be slow if not properly configured; the HP Web Jetadmin administrator should always formulate ranges that reflect only active portions of the network. IT or network administration staff should be consulted when formulating IP range information. Today, IP range set rotation is a manual process, but in the near future a feature will exist that automates this rotation using multiple discovery schedules. Finally, IP Range discoveries do not take large portions of network bandwidth on modern networks. 9 Acronyms MFPs: EWS: SNMP: WJA: Multifunction peripherals. Embedded Web Server. Simple Network Management Protocol HP Web Jetadmin, which is a simple peripheral management software application for remotely installing, configuring, and managing a wide variety of HP and non-hp network peripherals using only a standard Web browser. 10 Other Resources Web Jetadmin specifications, fact sheets, and download links can be found on the HP Web site: See the Technology Notes section of the site but also be sure to see the white paper that discusses HP Web Jetadmin Discovery features: Page 9