SMS: How Systems Management Server Network Discovery Discovers Clients with Static IP Addresses (228900)

SUMMARY

Microsoft Systems Management Server Network Discovery may not report discovery data for computers that have static IP addresses. Viewing the Netdisc.log (logging must be enabled via Systems Management Server Service Manager) reveals that the computer is found and it's IP address is identified, but a Data Discovery Record (DDR) is not written. A DDR is not written unless the subnet mask of the computer can be positively determined.

Systems Management Server Network Discovery can determine the subnet mask of the client from the following sources:

• A Microsoft DHCP Server. Network Discovery retrieves the active leases and defined subnet lists that have been configured on the DHCP server. Note that the Systems Management Server Service account requires at least Domain User access to the DHCP server. Also, if the Site Server is installed on a Windows NT Server with a static IP address, make sure that the IP address of the DHCP server has been entered in the DHCP tab of Network Discovery Properties. Site servers with a static IP address do not find the local DHCP server if the "Use local DHCP servers" box is checked but no DHCP servers have been entered.
• An SNMP agent. Make sure that the community name is specified correctly in the SNMP tab of Network Discovery Properties. Note that the site server's default gateway is automatically included in the list of SNMP devices Network Discovery contacts to gather information. Systems Management Server attempts to gather information about other SNMP devices on the network, but it may be necessary to add the IP address of SNMP devices (such as routers) to the SNMP Devices tab of Network Discovery Properties.
• The router ARP cache entry. To discover machines with static addresses, it is necessary to have an SNMP agent installed on the client, or the client needs to be in the local router's ARP cache. In general, entries only remain in the ARP cache anywhere from 60 seconds to about 10 minutes, depending on the router software and the TimeToLive value. Check the router configuration to determine its cache.

There are utilities available to view the ARP cache of a router such as the ARP command line utility. The following command should return the current contents of the router cache:

ARP -a routerIPaddress

Since entries do age out of the ARP cache, it may be necessary to schedule network discovery to run multiple times to find all machines. Also, if a machine is especially "quiet" it may not appear in the ARP cache of the local router. Any communication across a router, such as a ping to a remote network, will add the machine to the ARP cache of the router.

NOTE: When topology, topology and client, and topology, client and client operating system network discovery is enabled, Microsoft Windows 95, Windows 98, or Windows Millennium Edition clients only report discovery datas if they have File and Print sharing enabled.

Computers that have statically assigned addresses can be added to a DHCPs RESERVED list and be successfully discovered with Network Discovery. For additional information, click the article number below to view the article in the Microsoft Knowledge Base: