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Network discovery

Network discovery

Network Discovery discovers the internal IP networks and subnets within your organization.

Note: If you already know the IP address ranges in your network, it is not necessary to run Network Discovery. It is intended for organizations that do not have complete knowledge of the IP addresses available for Discovery in their networks.

How network discovery works

Discovery uses the information it gathers to update routers and Layer 3 switches in the CMDB. A single MID Server that begins its scan on a configurable list of starting (or seed) routers performs network Discovery. Typically, the starting routers are the default routers used by all the MID Server host machines in the network, but can be any designated routers. The MID Server uses the router tables on the starting routers to discover other routers in the network. The MID Server then spreads out through the network, using router tables it finds to discover other routers. It continues until all the routers and switches have been explored.

After running Network Discovery, convert the IP networks it finds into IP address Range Sets that you use in Discovery schedules to discover configuration items (CI).

Configure SNMP credentials or (optionally) SSH credentials. Port 161 must be open for SNMP access and port 22 or SSH access.

Network Discovery properties

The default values are correct for most discoveries. Navigate to Discovery Definitions > Properties to edit the properties.
Table 1. Network Discovery Properties
Property Description Default
BGP Router Exploration Disable Controls whether Network Discovery exploration of routers running the BGP protocol is disabled. Normally such exploration is disabled. Because of the huge size of BGP routing tables, and they operate at the edge of large networks where further network discovery would be irrelevant. This value should be set to no only when your organization uses BGP routers as edge routers between relatively small networks, like between buildings on a single campus. Yes
Maximum Netmask Size for Discoverable Networks (bits) The maximum number of bits in a regular netmask for networks discovered by Network Discovery. A regular netmask, is a netmask that can be expressed in binary as a string of ones followed by a string of zeroes. For example, 255.255.255.0 is regular, and 255.255.255.64 is irregular. Regular networks are commonly expressed like: 10.0.0.0/24, which means a network address of 10.0.0.0 with a netmask of 255.255.255.0. Larger bit numbers mean networks with smaller numbers of addresses in them. For example, the network 10.128.0.128/30 has four addresses in it: one network address (10.128.0.128), one broadcast address (10.128.0.131), and two usable addresses (10.128.0.129 and 10.128.0.130). Small networks are commonly configured in network gear to provide loopback addresses or networks used strictly by point-to-point connections. Since these sorts of networks generally do not need discovery by Network Discovery, it would be useful to filter them out. By setting this property to a value of 1 through 32, you can limit the sizes of regular networks that are discovered. Setting it to any other value causes all networks to be discovered. Irregular networks are always discovered. The default value is 28, which means that regular networks with 8 or fewer addresses are not discovered. 28
Network Router Selection Method This property controls the method used to decide which router should be selected as the router to be associated with a given IP Network. The possible values are:
  • First Router (the first router that discovers the network is associated).
  • Last Router (the last router that discovers the network is associated).
  • Most Networks (the router with the most attached networks is associated).]
  • Least Networks (the router with the least attached networks is associated).
Most Networks
Physical Interface Types A comma-separated list of interface types that should be considered physical for the purposes of network discovery. If a router (or device capable of routing) has an interface of this type, the networks connected to that interface are considered locally connected to that device. The default interface types include Ethernet, 802.11, and Token Ring types. Interface type numbers are defined in the SNMP MIB-2, specifically in OID 1.3.6.1.2.1.2.2.1.3. 6,117,9,71,209
Switch Interface Types Comma-separated list of interface types that is considered. Interface type numbers are defined in the SNMP MIB-2, specifically in OID 1.3.6.1.2.1.2.2.1.3. Devices with any interface types that do not appear in this list are classified as routers, when they have routing. A complete list of the interface type numbers may be found on the IANA web site, in the list of ifType-MIB Definitions. 7,8,9,26,53,62,69,71,78,115,117,209
Stale Network Discovery Threshold (Days) The number of days until discovered information about network gear is considered stale. Network discovery launches probes to freshen the information when:
  • A router or other device capable of routing has not been discovered.
  • Discovered information is stale.
Otherwise, it reuses the information that has already been discovered. If this number is negative, then any previously discovered information is always considered stale, and network discovery always launches probes to freshen the information.
-1
Network Discovery Debugging Enables extensive logging (for debugging purposes) of all network Discovery activities on the instance. Normally logging is set to yes by developers. Yes

Run network Discovery

Configure network Discovery from a Discovery schedule.

Before you begin

Configure SNMP credentials or (optionally) SSH credentials. Port 161 must be open for SNMP access and port 22 or SSH access.

Procedure

  1. Navigate to Discovery > Discovery Schedules.
  2. Click New and select Networks from the list in the Discover field.
  3. Select a MID Server.

    This field is mandatory.

  4. Complete the form, including the scheduling fields.
  5. Right-click in the header bar and select Save from the pop-up menu.

    The Related Links and related lists appear.

  6. Click Network Discovery Private IPs in Related Links to view the list of default private IP networks in the Discovery IP Ranges Related List.

    The default IP networks in this list are available to every Network Discovery you conduct and are sufficient for most discoveries.

  7. If your organization has additional private IP addresses, click New to add them.
    Figure 1. Private IP addresses
    Private IP addresses
  8. Add starting routers to the schedule in the Discovery Range Sets list.
    1. Click the Network Discovery Auto Starting Routers link to populate the list with the starting router for each MID Server in your network.
    2. Click Edit to add or delete routers from the list.
    Figure 2. Network Discovery schedule
    Network Discovery schedule
  9. Run Discovery manually, or through the scheduler.

Convert IP networks into Discovery range sets

After you conduct a network Discovery, you must convert the IP networks that were found into range sets for use in discovering other devices.

Before you begin

Role required: agent_admin or admin

Procedure

  1. Navigate to Discovery > Output and Artifacts > IP Networks.
  2. Click New to add an IP network.
  3. Ensure that the following field values are provided:
    • State: Ready
    • Discover: selected (true)
    • Router: Select a router from the list. This field must not be empty.
      If your IP Networks were created through network Discovery, then these fields are populated automatically in the IP Networks related list. However, if you entered the IP Networks manually, and you want to convert your IP Networks into range sets manually, you must edit these fields accordingly.
      Figure 3. IP network form
      IP network form
  4. Click Update to return to the list of IP Networks.
  5. In Related Links, click Create Range Sets.
    Use this feature to convert all the IP networks in the list into range sets.
    Figure 4. IP network list
    IP network list

    The Discovery Status page appears, displaying the progress of the conversion. The system increments the Started and Completed count of IP networks, until all the networks are converted.

What to do next

Add discovery range sets to Discovery schedules.

Add a Discovery range set to a Discovery schedule

After creating discovery range sets from a network discovery, add the sets to a discovery schedule. This process narrows down the range of IP addresses that Shazzam probes can scan. You can also add a behavior.

Before you begin

Role required: agent_admin or admin

Procedure

  1. Open a Discovery schedule.
  2. In the Discovery Range Sets related list, click Edit to add an existing range set and use the slushbucket to add the range set.
  3. On the Discovery schedule form, click the name of the range set under the Range column in the Discovery Range Sets related list.
  4. On the Discovery Range Set form, add a Discovery behavior if necessary. You can also activate or deactivate the range set for this schedule.
  5. Right-click the header, and then click Save.