Table Of Contents
Introduction
This chapter introduces Virtual Network Elements (VNEs) and describes the types of information available in this Guide. It includes the following sections:
Introduction to VNEs
VNEs (Virtual Network Elements) are independent software processes that run on the Cisco ANA Unit Servers. Each VNE is assigned to manage a single network element (NE) using the NE's management interfaces (for example, SNMP and/or Telnet). The VNEs maintain a live model, or abstraction, of each NE and the entire network.
As the VNE loads, it starts investigating the NE and automatically builds a live model of the NE, including its physical and logical inventory, its configuration and its status. After modeling the NE, the VNE begins negotiating with peer VNEs, which represent the peer NEs, in order to determine NE connectivity and topology at different layers. This model of the network topology, NE state, and NE inventory is constantly being updated by the VNEs, which track every change that occurs in the NEs and the network.
The VNEs communicate between themselves to analyze end-to-end flows, which provide information for root-cause and impact analysis, service path tracing, and more.
Understanding the Tables
The following legends describe key information that can be found in the VNE support information chapters in this Guide:
Certification Level Legend
Table 1 describes the meaning of the certification levels found in the VNE support information tables in this Reference Guide.
Table 1 Certification Level Legend
N
Not supported.
S
Supported.
V
Verified.
Polling Interval Legend
In Cisco ANA, the VNEs poll the NEs to discover and display accurate and up-to-date information of the network. The system periodically triggers polling at set intervals. The polling rates can be customized or optimized by the administrator.
Cisco ANA provides the ability to fine-tune the frequency in which information is retrieved from the NEs in order to enable a high degree of control and flexibility over the amount of network traffic used by the various VNEs. Different polling intervals can be set for gathering information for:
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Status—Sets the polling rate for status-related information, such as device status (up/down), port status, admin status and so on. The information is related to the operational and administrative status of the NE.
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Note
In addition to the defined polling intervals, the VNEs implement adaptive polling ensuring that the element is not overloaded. Checking the device CPU may defer specific polls in order to avoid an additional load on the NE.
The user can define polling profiles by setting customized polling intervals which can be applied to managed NEs. The VNE then polls the network element according to the preset values. This ensures polling of devices for different information consistently and in accordance with technical and business requirements.
Core devices can be assigned to a polling group (all devices use the same polling profile) that specifies a higher frequency for status but a lower frequency for configuration-related information while edge or access devices can be polled more frequently for system and configuration-related information. Managed network service operators for example, can use polling groups to reflect their agreement with customers so that premium customer devices are polled more frequently than normal devices.
For the administrator's convenience, Cisco ANA includes the pre-configured polling group "default" which cannot be deleted. The default polling group includes the following settings:
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Scheme Legend
Schemes affect the implementation of VNE modeling components. This enables the administrator to define different behavior for some NEs, for example, some NEs poll only with SNMP; others poll with Telnet. Soft properties and activation scripts are also attached to a specific scheme.
Table 2 describes the schemes that are supported in Cisco ANA 3.6. This information is listed in the Scheme column, which can be found in the VNE support information tables in this Reference Guide.
Having two schemes provides users with more flexibility to specify which registrations the VNEs modeling their routers will use. A registration is how the VNE queries a live device for information. In previous releases, all router VNEs used to poll IP/VPN related commands for PEs. With Cisco ANA 3.6, users can designate a VNE as a core router by setting it to work with the IP-Core scheme, or an edge router by setting it to work with the Product scheme.
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Expedite Legend
Table 3 describes the meaning of the Expedite column found in the service event (service alarm) tables in this Reference Guide.
