Cisco Element Manager System Installation and Configuration Guide, 3.1
Auto Discovery
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Auto Discovery

Table Of Contents

Auto Discovery

Mechanisms for Discovering Devices

Auto Discovery Process

Firewall Configurations

Scheduling Auto Discovery

Auto Discovery

The Cisco EMF Auto Discovery application allows you to examine the network for IP and SNMP devices and create a managed object for each new device discovered. Auto Discovery can be opened from the Cisco EMF Launchpad window or from a pop up menu available on a selected object. The Cisco EMF User Guide provides more information.

Note Cisco EMF supports both SNMPv1 and SNMPv2c.

The mechanisms used for discovering devices and the Cisco EMF Auto Discovery process are described in this chapter.

Auto Discovery can be scheduled to start at a particular time and for a specified period to monitor parts of the network for the addition of new devices. This chapter details how this is set up.

Mechanisms for Discovering Devices

The Auto Discovery application can use three different mechanisms for discovering devices:

IP—ICMP pings are used to find devices in a given IP address range. This allows Cisco EMF to find which IP devices exist, but does not enable it to discover what kind of devices they are.

SNMP—SNMP get requests are used to find devices in a given IP address range. Several SNMP community strings can be used so equipment with different community strings can be discovered in the same discovery session. The SNMP information returned by devices is used to determine the types of devices that have been found.

IP and SNMP—ICMP pings are used to find devices and then SNMP requests are used to interrogate the devices to find out what kind of devices they are. This is the default mechanism.

The Auto Discovery application can discover devices on more than one subnetwork by using multi-hop discovery. This option is available when using SNMP or IP and SNMP discovery. When Cisco EMF discovers a device that is connected to more than one network, it can run Auto Discovery on the next network. It does this if the hop count is greater than zero. The next network is then discovered with hop count minus one.

When Auto Discovery is launched as a service from a selected IP manageable object, the discovery range, by default, is related to the IP address of the launch object.

An option is available to specify the physical location where discovered objects will be created. This is particularly useful when using Auto Discovery with Element Managers.

Auto Discovery Process

Auto Discovery proceeds with IP pings (ICMP echo requests) first (if IP is selected), followed by SNMP GETs of sysDescr and sysObjectId (if the ping was successful and SNMP is selected or SNMP only is selected).

Only devices within the selected range should be pinged, unless however, one of the devices discovered is a router. For example, if a router has three ports with IP addresses,, and, the system automatically pulls the network address entry table and creates network objects for the networks on the other interfaces. As Cisco EMF is discovering on network, it finds the first interface. It also finds that the device is a router (it has IP forwarding configured), so it finds the other interfaces and creates networks for and, as well.

The hop count field specifies how many times auto discovery should begin on a new subnet. If Cisco EMF discovers a device with multiple IP interfaces, it automatically starts auto discovery on the other interfaces if the hop count is greater than zero; the address range is the entire subnet for that interface and the hop count is decremented each time this occurs.

If no response to the ping is received within the timeout period, the operation is tried again, up to the number of times specified in ping retries.

For SNMP gets, all provided community strings are tried until one succeeds or the list is exhausted.

Note A Cisco EMF object is created for every device which responds, even for those which only respond to pings and not SNMP get requests. If you only want objects which responded to the SNMP get requests to be created, then use the SNMP only discovery method.

Firewall Configurations

To manage or auto-discover networks, the following traffic must be allowed through any firewall between Cisco EMF and the agents:

1. SNMP traffic of protocol type UDP on Port 161 & 162

2. Telnet traffic of protocol type TCP on Port 23

3. tftp traffic of protocol type UDP on Port 69

4. icmp traffic of protocol type TCP and UDP on Port 7

Scheduling Auto Discovery

Auto Discovery can be automatically scheduled by editing the discoverySchedules file in the <CEMF_ROOT>/config/discoverySchedules directory, where <CEMF_ROOT> is the Cisco EMF installation directory. This allows you to specify the IP address range, communities to query within that network, the number of hops, the number of ping and SNMP retries, the discovery method, and time and period values.

Note You do not have to set up a schedule. Auto Discovery can be opened from Network Maps or the Object Group Manager as described earlier.

Step 1 Using a Text Editor, open the discoverySchedules file.You can edit existing schedules or create new schedules as required. For example, to create a schedule for a second network you would add the name of the schedule, for example sched2 to the schedules line, and create entries in the file with sched2 preceding each line.

Note To stop a schedule, remove the name of the schedule and the associated entries in the file. When all changes have been made, save the files and close the Text Editor. Run the files using the <CEMF_ROOT>/bin/reinit_discovery program.

Step 2 The StartAddress and EndAddress specify the network you want to auto discover. Enter the appropriate IP addresses.

Step 3 In Communities, enter the relevant SNMP community names, in a comma separated list.

Step 4 Enter the number of hops. This is a value between 0 and 16. The hop count should be left at zero when Auto Discovery using IP only is selected.

Step 5 Enter the number of ping retries. This is a value between 0 and 10.

Step 6 Enter the number of SNMP retries. This is a value between 0 and 10.

The DiscoveryMethod options are as follows:

0     IP only

1     SNMP only

2     IP & SNMP

Step 7 Enter the start time, using the 24 hour clock notation. This is the time the schedule starts.

The period can be defined by a number and a keyword - minutes or hours or days. The period is each time auto discovery is scheduled to occur

The following example shows schedules for two networks:


schedules = sched1, sched2

sched1StartAddress =
sched1EndAddress =
sched1Communities = public, private
sched1Hops = 0
sched1PingRetries = 0
sched1SnmpRetries = 0
sched1DiscoveryMethod = 2
sched1StartTime = 14:09:00
sched1Period = 5 minutes
sched1SnmpTimeout = 10 seconds
sched1ParentPath = Physical:/

sched2StartAddress =
sched2EndAddress =
sched2Communities = public, private
sched2Hops = 0
sched2PingRetries = 0
sched2SnmpRetries = 0
sched2DiscoveryMethod = 2
sched2StartTime = 11:30:00
sched2Period = 7 days
sched2SnmpTimeout = 10 seconds
sched2ParentPath = Physical:/Site-1/

Step 8 When all changes have been made, save the files and close the Text Editor. Run the files using the <CEMF_ROOT>/bin/reinit_discovery program.

The discoveryScheduler.log file in <CEMF_ROOT>/logs informs you of the present scheduled settings, the progress, and reasons for the scheduling not starting, if applicable.