Information About Device Discovery
This section includes the following topics:
Device Discovery
The Device Discovery feature creates devices in DCNM-LAN by connecting to a Cisco NX-OS device and retrieving data from the device, including its running configuration. DCNM-LAN can also discover Cisco NX-OS devices and network servers that are neighbors of the first device, which is known as the
seed device
.
Note Staring from Cisco NX-OS Release 5.2.2(a) the Cisco DCNM-LAN supports the discovery of the following modules:
-
N7K-F248XP-25 Line Card
-
N55-M16FP 16-Port FC GEM
-
N7K-C7010-FAB2 Fabric 2 module
-
N7K-C7018-FAB2 Fabric 2 module
-
N55-D160L3-V2 Daughter Card
-
N55-M160L3-V2 Line Card
-
N3K-C3048TP-1GE Layer 3 switch
-
N3K-C3016Q- 40GE Layer 3 switch
If the device supports virtual device contexts (VDCs), DCNM-LAN retrieves the running configuration of each VDC that is configured on the physical device. DCNM-LAN displays each VDC as a device, including the default VDC. If the Cisco NX-OS device has only the default VDC, then device discovery creates only one device in DCNM-LAN.
When DCNM-LAN connects to a device to retrieve its configuration, it uses the XML management interface, which uses the XML-based Network Configuration Protocol (NETCONF) over Secure Shell (SSH). For more information, see the
Cisco NX-OS XML Interface User Guide
.
Discovery Protocols
DCNM-LAN uses a variety of protocols to discover devices and servers in your data center network. This section includes the following topics:
Cisco Discovery Protocol
Device discovery uses the Cisco Discovery Protocol (CDP) to find devices that are connected to the initial device in the discovery process. CDP exchanges information between adjacent devices over the data link layer. The exchanged information is helpful in determining the network topology and physical configuration outside of the logical or IP layer.
CDP allows DCNM-LAN to discover devices that are one or more hops beyond the seed device in the discovery process. When you start the discovery process using the Device Discovery feature, you can limit the number of hops that the discovery process can make.
After DCNM-LAN discovers a Cisco NX-OS device using CDP, it connects to the device and retrieves information, such as the running configuration of the device. The information collected allows DCNM-LAN to manage the device.
DCNM-LAN supports CDP hops on some Cisco switches that run Cisco IOS software. Although DCNM-LAN cannot manage these devices, the Topology feature allows you to see unmanaged devices and the CDP links between unmanaged devices and managed devices.
Link Layer Discovery Protocol
Device discovery uses Link Layer Discovery Protocol (LLDP) to discover the network adapters of servers that are connected to Cisco NX-OS devices. For more information, see Chapter18, “Configuring Network Servers”
Fibre Channel
To discover network elements in a storage area network (SAN), DCNM-LAN uses Fibre Channel. DCNM-LAN can discover SAN switches, servers, and storage arrays.
Credentials and Discovery
Device discovery requires that you provide a username and password for a user account on the seed device. To successfully complete the discovery of a Cisco NX-OS device, the user account that you specify must be assigned to either the network-admin or the vdc-admin role.
If you want to discover devices that are one or more hops from the seed device, all devices in the chain of hops must be configured with a user account of the same username and password. All Cisco NX-OS devices in the chain of hops must assign the user account to the network-admin or the vdc-admin role.
Discovery Process
DCNM-LAN discovers devices in several phases, as follows:
1. CDP neighbor discovery—Discovers the topology of the interconnected devices, beginning with the seed device and preceding for the number of CDP hops specified when you initiate discovery.
2. Supported device selection—Determines which of the discovered devices are supported by DCNM-LAN. Discovery continues for the supported devices only.
3. Inventory discovery—Discovers the inventory of the devices selected in the previous phase. For example, if the device is a Cisco Nexus 7000 Series switch, inventory discovery determines the supervisor modules, I/O modules, power supplies, and fans. If the device is a Cisco Nexus 1000V switch, inventory discovery finds the Virtual Supervisor Module and Virtual Ethernet Modules.
4. Device configuration discovery—Discovers the details of feature configuration on each device, such as interfaces, access control lists, and VLANs.
5. Network discovery—Associates network features with the device configuration details discovered in the previous phase.
Cisco NX-OS System-Message Logging Requirements
To monitor and manage devices, DCNM-LAN depends partly on system messages that it retrieves from managed devices. This section describes the system-message requirements that all Cisco NX-OS devices must meet before they can be managed and monitored by DCNM-LAN.
This section includes the following topics:
Interface Link-Status Events Logging Requirement
Devices must be configured to log system messages about interface link-status change events. This requirement ensures that DCNM-LAN receives information about interface link-status changes. The following two commands must be present in the running configuration on the device:
-
logging event link-status enable
-
logging event link status default
To ensure that these commands are configured on the device, perform the steps in the “Verifying the Discovery Readiness of a Cisco NX-OS Device” section.
Logfile Requirements
Devices must be configured to store system messages that are severity level 6 or lower in the log file.
Although you can specify any name for the log file, we recommend that you do not change the name of the log file. When you change the name of the log file, the device clears previous system messages. The default name of the log file is “messages.”
If you use the default name for the log file, the following command must be present in the running configuration on the device:
logging logfile messages 6
To ensure that this command is configured on the device, perform the steps in the “Verifying the Discovery Readiness of a Cisco NX-OS Device” section.
Logging Severity-Level Requirements
DCNM-LAN has minimum severity level requirements for some Cisco NX-OS logging facilities. All enabled features on a Cisco NX-OS have a default logging level. The logging level required by DCNM-LAN varies per logging facility but is often higher than the default logging level in Cisco NX-OS. For more information, see the “Automatic Logging-Level Configuration Support” section.
Automatic Logging-Level Configuration Support
DCNM-LAN provides support for automatic logging level configuration for all supported Cisco NX-OS releases with the exception of Cisco NX-OS Release 4.0, which is available on Cisco Nexus 7000 Series switches only. This section describes how DCNM-LAN supports automatic logging-level configuration. For information about manually configuring logging levels for Cisco NX-OS Release 4.0, see the “Verifying the Discovery Readiness of a Cisco NX-OS Device” section.
During Device Discovery
During device discovery, if DCNM-LAN finds that a logging level on a discovered device is below the minimum logging-level requirement for that logging facility, DCNM-LAN raises the logging level to meet the minimum requirement. If logging levels meet or exceed the requirements, DCNM-LAN does not change the logging levels during discovery.
At Feature Enablement in the DCNM-LAN Client
If you use the DCNM-LAN client to enable a feature on a device and the default logging level for the feature does not meet the minimum requirement, the DCNM-LAN client warns you that it will configure the logging level on the device to meet the requirement. If you reject the logging level change, DCNM-LAN does not enable the feature.
During Auto-Synchronization with Managed Devices
If you use another means, such as the command-line interface (CLI), to enable a feature on a managed device and the default logging level for the feature does not meet the minimum requirement, DCNM-LAN automatically configures the logging level to meet the requirement after DCNM-LAN detects that the feature is enabled.
If you use the CLI or any other method to lower a logging level below the minimum requirement of DCNM-LAN, after DCNM-LAN detects the logging level change, it changes the state of that device to unmanaged. When this occurs, the Devices and Credentials feature shows that logging levels are the reason that the device is unmanaged. You can use the Devices and Credentials feature to discover the device again. During rediscovery, DCNM-LAN sets logging levels that do not meet the minimum requirements.
VDC Support
When DCNM-LAN discovers a Cisco NX-OS device that supports VDCs, it determines how many VDCs are on the Cisco NX-OS device. In DCNM-LAN, each VDC is treated as a separate device. The status of each VDC is tracked separately and you can configure each VDC independently of other VDCs on a Cisco NX-OS device.
Before discovering a Cisco Nexus 7000 Series device that has nondefault VDCs, ensure that each VDC meets the prerequisites for discovery. For more information, see the “Prerequisites for Device Discovery” section.
Performing Device Discovery
This section includes the following topics:
Verifying the Discovery Readiness of a Cisco NX-OS Device
Before you perform device discovery with DCNM-LAN, you should perform the following procedure on each Cisco NX-OS device that you want to manage and monitor with DCNM-LAN. This procedure helps to ensure that device discovery succeeds and that DCNM-LAN can effectively manage and monitor the device.
Note If you are preparing a physical device that supports virtual device contexts (VDCs), remember that DCNM-LAN considers each VDC to be a device. You must verify discovery readiness for each VDC that you want to manage and monitor with DCNM-LAN.
DETAILED STEPS
Step 1 Log into the CLI of the Cisco NX-OS device.
Step 2 Use the
configure terminal
command to access global configuration mode.
Step 3 Ensure that an RSA or DSA key exists so that secure shell (SSH) connections can succeed. To do so, use the
show ssh key rsa
or
show ssh key dsa
command.
If you need to generate a key, use the
ssh key
command.
Note You must disable the SSH server before you can generate a key. To do so, use the no feature ssh command.
Step 4 Ensure that the SSH server is enabled. To do so, use the
show ssh server
command.
If the SSH server is not enabled, use the
feature
ssh
command to enable it.
Step 5 Ensure that CDP is enabled globally and on the interface that DCNM-LAN uses to connect to the device. Use the
show run cdp all
command to see whether CDP is enabled.
Step 6 Verify that the
logging event link-status default
and
logging event link-status enable
commands are configured.
switch(config)# show running-config all | include "logging event link-status" logging event link-status default logging event link-status enable
If either command is missing, enter it to add it to the running configuration.
Note The logging event link-status enable command is included in the default Cisco NX-OS configuration. The show running-config command displays the default configuration only if you use the all keyword.
Step 7 Verify that the device is configured to log system messages that are severity 6 or lower.
Note The default name of the log file is “messages”; however, we recommend that you use the log-file name currently configured on the device. If you change the name of the log file, the device clears previous system messages.
switch(config)# show running-config all | include logfile logging logfile logfile-name 6
If the
logging logfile
command does not appear or if the severity level is less than 6, configure the
logging logfile
command.
switch(config)# logging logfile logfile-name 6
Step 8 If the device is a Cisco Nexus 7000 Series switch that is running Cisco NX-OS Release 4.0, you must manually verify that the logging level configuration of the device meets the DCNM-LAN logging level requirements. To do so, follow these steps:
a. Determine which nondefault features are enabled on the device.
switch(config)# show running-config | include feature
b. View the logging levels currently configured on the device. The
show logging level
command displays logging levels only for features that are enabled. The Current Session Severity column lists the current logging level.
switch(config)# show logging level Facility Default Severity Current Session Severity -------- ---------------- ------------------------
Note You can use the show logging level command with the facility name when you want to see the logging level of a single logging facility, such as show logging level aaa.
c. Determine which logging levels on the device are below the minimum DCNM-LAN required logging levels. To do so, compare the logging levels displayed
on page 1-9
to the minimum DCNM-LAN required logging levels that are listed in
Table 1-2
.
d. For each logging facility with a logging level that is below the minimum DCNM-LAN required logging level, configure the device with a logging level that meets or exceeds the DCNM-LAN requirement.
switch(config)# logging level facility severity-level
The
facility
argument is the applicable logging-facility keyword from
Table 1-2
, and
severity-level
is the applicable minimum DCNM-LAN required logging level or higher (up to 7).
e. Use the
show logging level
command to verify your changes to the configuration.
Step 9 Copy the running configuration to the startup configuration to save your changes.
switch(config)# copy running-config startup-config [########################################] 100%
Discovering Devices
You can discover one or more devices. When a discovery task succeeds, DCNM-LAN retrieves the running configuration and status information of discovered Cisco NX-OS devices.
Use this procedure for the following purposes:
-
To discover devices that are not currently managed by DCNM-LAN. For example, you should use this procedure when DCNM-LAN has not yet discovered any devices, such as after a new installation.
-
To discover devices that you have added to your network without rediscovering devices that DCNM-LAN already has discovered.
-
To rediscover the topology when CDP links have changed without rediscovering devices that DCNM-LAN has already discovered.
Note You must successfully discover a Cisco NX-OS device before you can use DCNM-LAN to configure the device.
BEFORE YOU BEGIN
Ensure that you have configured the Cisco NX-OS device so that the DCNM-LAN server can connect to it and successfully discover it. For more information, see the “Verifying the Discovery Readiness of a Cisco NX-OS Device” section.
Determine the IPv4 address of the device that you want DCNM-LAN to connect to when it starts the discovery task. This is the seed device for the discovery.
Determine whether you want to discover devices that are CDP neighbors of the seed device. If so, determine the maximum number of hops from the seed device that the discovery process can make.
Note The discovery process can perform complete discovery of neighbors only if the neighboring devices are configured with the same credentials as the seed device.
DETAILED STEPS
Step 1 From the Feature Selector pane, choose
DCNM Server Administration > Device Discovery
.
The discovery tasks appear in the Discovery Tasks area of the Contents pane.
Step 2 In the Seed Device field, enter the IPv4 address of the device that you want DCNM-LAN to connect to when it starts the discovery task. Valid entries are in dotted decimal format.
Step 3 In the User Name field, enter the username of a user account on the device. The user account must have a network-admin or vdc-admin role.
Step 4 In the Password field, enter the password for the user account that you entered in the User Name field.
For Catalyst 6500 devices, enter the enable password in the Enable Password field to allow for IOS privileged EXEC mode commands.
Step 5 (Optional) If you want DCNM-LAN to discover devices that are CDP neighbors of the seed device, in the Maximum Hops of Neighbors to Discover field, enter the desired maximum number of hops. By default, the maximum hops is 0 (zero).
Step 6 Ensure that
Rediscover Configuration and Status for Existing Devices
is unchecked. By default, this check box is unchecked.
By leaving this check box unchecked, you enable DCNM-LAN to use previously discovered devices as CDP hops without retrieving their running configuration and status information.
Step 7 Click
Start Discovery
.
After a short delay, the discovery task appears at the bottom of the list of tasks in the Discovery Tasks area. DCNM-LAN updates the task status periodically.
Step 8 Wait until the status for the task is Successful. This step may take several minutes.
After the status is Successful, you can use DCNM-LAN to configure and monitor the discovered devices.
You do not need to save your changes.
Rediscovering Devices
You can rediscover one or more devices.
Note Rediscovery replaces any configuration data that DCNM-LAN has for a Cisco NX-OS device with the configuration data retrieved during the rediscovery. If you need to discover one or more devices without retrieving configuration and status information for already discovered devices, see the “Discovering Devices” section.
You must successfully discover a Cisco NX-OS device before you can use DCNM-LAN to configure the device.
DETAILED STEPS
Step 1 From the Feature Selector pane, choose
DCNM Server Administration > Device Discovery
.
The discovery tasks and their status appear in the Discovery Tasks area of the Contents pane.
Step 2 In the Seed Device field, enter the IPv4 address of the device that you want DCNM-LAN to connect to when it starts the discovery task. Valid entries are in dotted decimal format.
Step 3 In the User Name field, enter the username of a user account on the device. The user account must have a network-admin or vdc-admin role.
Step 4 In the Password field, enter the password for the user account that you entered in the User Name field.
For Catalyst 6500 devices, enter the enable password in the Enable Password field to allow for IOS privileged EXEC mode commands.
Step 5 (Optional) If you want DCNM-LAN to rediscover devices that are CDP neighbors of the seed device, in the Maximum Hops of Neighbors to Discover field, enter the desired maximum number of hops. By default, the maximum hops is 0 (zero).
Step 6 Check
Rediscover Configuration and Status for Existing Devices
. By default, this check box is unchecked.
By checking this check box, you enable DCNM-LAN to replace any configuration and status information that it has about a previously discovered device with the running configuration and status information retrieved from the device.
Step 7 Click
Start Discovery
.
After a short delay, the discovery task appears at the bottom of the list of tasks in the Discovery Tasks area. DCNM-LAN updates the task status periodically.
Step 8 Wait until the status for the task is Successful. This step may take several minutes.
After the status is Successful, you can use DCNM-LAN to configure and monitor the discovered devices.
You do not need to save your changes.