Understanding Network Discovery

Network discovery is the process that ZENworks for Servers 3 uses to scan your network and discern its topology. This section discusses the specific components that are involved in network discovery, the process they use to discover your network topology, and the types of devices that are discovered.

Understanding the Discovery Components

To understand network discovery, you need to understand the discovery components that are running on the ZENworks for Servers 3 management servers. The discovery components are responsible for scanning your network for devices, collecting data, and transferring that data to NetExplorer.

NetExplorer is the main network discovery module. It is responsible for coordinating the discovery components and collecting their data, which is consolidated into a database where it can be managed and used.

The following sections discuss the main discovery components that make up network discovery: the discovery software, the consolidator software, and the Atlas Manager.

About the Discovery Software

The discovery software is software that resides on the ZENworks management server. The discovery software is responsible for polling the network and collecting data about devices that exist on the network. The data collected by the discovery software is stored in the SYS:\SYSTEM\NETXPLOR.DAT file.

The discovery software comprises the following NLMs that run on the discovery server:

• NXPIP.NLM. Responsible for discovering IP routers on IP networks and sending IP router information to the discovery. It communicates directly with IPCACHE and indirectly with IPGROPER, which are other discovery modules running on the server, to obtain information.

• NXPIPX.NLM. Responsible for discovering various NetWare systems on IPX networks and sending information about systems to NetExplorer.

• IPGROPER.NLM. Responsible for detecting IP host addresses and services on an IP network, including DHCP services, DNS names, HTTP, SMTP, FTP, SMTP, and Telnet.

• NXPLANZ.NLM. Responsible for communicating with traffic analysis agents for NetWare and NT to gather information about all systems communicating on their segments.

NOTE

ZENworks for Servers 3 discovery software uses its server and traffic management agents to obtain discovery information. You should use these agents throughout your network to improve the speed, reliability, and accuracy of the topology maps.

The server management and traffic analysis agents for NetWare use the Service Advertising Protocol (SAP) to identify themselves to other components. To enable the network discovery component to receive the SAP packets that identify manageable devices on the network, configure your routers so that they are not filtering out the needed SAP packets. Use Table 9.1 to configure your routers.

Table 9.1. SAP Numbers for ZENworks Management Devices

COMPONENT	SAP (DECIMAL)	SAP (HEXADECIMAL)
NetExplorer	567	237
NetWare Management Agent	635	27B
NT Management Agent	651	28B
Traffic Analysis Agent	570	23A
Print server	7	7
NetWare server	4	4

Understanding the Consolidator Software

Like the discovery software, the consolidator software resides on the ZENworks for Servers 3 management server. The consolidator takes the information that is collected by the discovery software, cleans it up, and stores it in the ZENworks for Servers 3 database for later use.

The following is a list of tasks performed by the consolidator to collect network information and store it in the ZENworks for Servers 3 database:

• Reads the NETXPLOR.DAT file

• Interprets the records in the NETXPLOR.DAT file

• Verifies that the device is not already discovered

• Queries the bridge management information base (MIB) on IP networks to discover the MAC addresses of all systems on a port

• Uses the SN3 agent to get the NDS name for network objects

• Determines whether additional attributes exist in the discovered device

• Writes the consolidated information to the ZENworks database

Discussing the Atlas Manager

The Atlas Manager consists of components that exist both on a server and a client. These components are responsible for reading the ZENworks for Servers 3 database, creating a topology database, and enabling a user to browse and manage the network topology.

The server component runs on the ZENworks for Servers 3 management server, where it retrieves discovery information from the ZENworks for Servers 3 database. It then uses that information to create a topology database.

After the topology database is created, the client component of the Atlas Manager can communicate with the Atlas Manager server component. The client component requests topology information from the server component to display topology maps at the client management console. When a user modifies the topology from the client management console, the client component transfers those changes to the server component. The server component then makes the appropriate changes to the topology database.

NOTE

For changes made to the network topology from the client to take effect, you must save the database.

Examining Related Components

Other components exist that are not directly discovery components, but are used during the discovery process. The following are components that NXPIP.NLM, NXPIPX.NLM, and NXPLANZ.NLM use during the discovery process to obtain a full network topology:

• Traffic analysis agent. The traffic analysis agent discovers all devices on the segments that it is monitoring. The NXPLANZ component uses SNMP to query servers running the traffic analysis agent about the devices on their segments.

• Server management agent. The server management agents respond to SNMP queries from the NXPIPX component. They provide NXPIPX with usernames and addresses of the workstations that are attached or logged in to them.

• NetWare Servers. NetWare Servers have internal routing tables stored in their memory. The NXPIPX components query NetWare servers for the information in those tables.

Introducing the Database Object Editor

ZENworks for Servers 3 provides a Database Object Editor (DOE) to supplement the discovery system. Discovery cannot always discover every entity on your network, or it might display incorrect information about some of the entities on your network. The DOE enables you to add the missing entities into the database or edit incorrect information of the entities.

Understanding the Discovery Process

Now that you understand the components that make up network discovery, you need to understand the process that they go through to query your network, collect data about manageable devices, and build a database.

Network discovery occurs in cycles. Each cycle is the process by which one of the discovery modules identifies every device possible, one time. The initial cycle is the first cycle that discovery makes. Although the initial cycle is enough to begin building a topology map, it usually takes several passes to complete the entire network topology.

During the initial discovery cycle, the discovery modules run sequentially; however, after the initial pass, they run independent of each other. The time it takes each module to complete a cycle varies depending on the number of new devices it discovers. When new information is discovered, the discovery modules transfer the data to the NetExplorer, which stores it in a file. Each cycle has the potential to provide the key information NetExplorer needs to identify the device and add it to the database.

The following sections discuss the discovery cycles for each of the discovery modules.

NXPIP

The first sequence in the NetExplorer discovery cycle involves the discovery of IP routers. NXPIP locates its local router by using TCP/IP configuration information and then queries the router for the identity of other routers on the network. NXPIP then queries the MIBs on those routers and collects the IP addresses, interface types, and MAC addresses.

NXPIPX

The NXPIPX discovery begins after NXPIP has completed its first cycle. NXPIPX discovery begins at the management server and uses SNMP, RIP, IPX, and SPX diagnostics to discover attached IPX devices.

NXPIPX begins by examining its own server's routing table and discovers the names of other servers. It then queries each of those servers and repeats the process until no new servers are found.

NXPIPX also reads the connection table of each NetWare server to determine which NetWare clients are logged in to which servers. NXPIPX sends IPX diagnostics packets to the clients to collect additional information about them. NXPIPX also discovers IPX routers in your network.

NOTE

If your clients have IPX diagnostics turned off, they will not be discovered.

NXPLANZ

NXPLANZ begins querying after NXPIPX has completed its first cycle. NXPLANZ obtains a list of all traffic analysis agents from NXPIPX and then uses SNMP to query all servers with the traffic analysis agents loaded. It reads the list of workstations that those servers have observed communicating on the network.

NOTE

At least one server per network segment should be running the traffic analysis agent for the discovery to be complete.

SNMP Community Name

NetExplorer uses the configured community names from NXPCON each time it attempts to access a system by using SNMP. When it encounters a new system, it runs through the list of names configured in NXPCON until it receives a successful response. After the community name is found, it is stored for later reference.

Understanding What Is Discovered

Now that you understand the process that ZENworks for Servers 3 uses to discover devices on your network, you may want to know what types of devices are being discovered. The devices that are discovered by ZENworks for Servers 3 can be categorized into either network systems or network segments. The following sections discuss the devices that are discovered by ZENworks for Servers 3.

Network Systems

The first category of device that the ZENworks for Servers 3 discovery process detects is network systems. Network systems are manageable devices with addresses and/or services associated with them. Network discovery queries the network by using addressing and service requests to find these devices.

The following is a list of network systems that are discovered by ZENworks for Servers 3:

• NetWare file server. Service type 4. Discovered by NXPIPX.

• IPX router. Systems with more than one LAN adapter connected to different IPX networks.

• IP router. System that is configured as an IP router.

• NetWare print server. Service type 7.

• NetWare client workstation. Systems that respond to IPX diagnostic requests as IPX workstations.

• SFT III engines. Discovered by the NXPIPX discovery module. Provides diagnostic information.

• NetWare Management Agent. Service type 563.

• NetWare LANalyzer Agent. Service type 570.

• NetWare Management Agent for NT. Service type 651.

• Network printers. Discovered if the printer generates a known service type.

• NetWare Connect. Service type 590.

• NetWare communications server. Used by NetWare for SAA management products. Service type 304.

• Management server. Server running discovery modules. Service type 567.

• Other systems. Any systems that are connected on a segment that is being monitored by the traffic analysis agent.

Network Segments

The other category of device that the ZENworks for Servers 3 discovery process detects on your network is network segments. Network segments are the communication framework that lies underneath the network systems. The network systems use this framework to communicate with each other. Network discovery detects the different network segment topologies and stores that information in the database. The following sections discuss the different types of network segments that are discovered by ZENworks for Servers 3.

LAN and WAN Segments

ZENworks for Servers 3 discovers the typical LAN and WAN segments on your network, provided that they respond with an interface type from the MIB-II RFC 1573 specification. The following is a list of segments that are known by the ZENworks for Servers 3 database:

• ATM. ATM

• FDDI. LAN

• Ethernet. LAN

• Token ring. LAN

• X.25. WAN

• PPP. WAN

• Frame_Relay. WAN

Source-Route Bridged Token Rings

ZENworks for Servers 3 network discovery also finds source-route bridged token ring segments. How well these segments are discovered and how they appear in your topology map depends on where traffic analysis agents are installed on each of the bridged rings.

NOTE

We suggest that you have the traffic analysis agent loaded on at least one NetWare server on each of your bridged rings to provide you with the best discovery and manageability through ZENworks for Servers.

Transparent Bridges

Network discovery is unable to fully discover transparent bridges. Therefore, because they have the same network number, it consolidates groups of transparently bridged segments into a single segment on the topology maps.

Configuration Changes

Network discovery can detect most changes in your network topology and relay those changes to the Atlas. But if you remove a device from the network, discovery does not detect the removed device unless it is moved to another location in the network.