Hosts and Attributes¶
Zones are groupings of Hosts. They can be used for displaying a group together or for making a set of hosts visible.
Hosts are the devices that you want to manage. They are essentially something that has an IP address (either IPv4 or IPv6) and generally would also have some sort of SNMP Agent. The Agent is not essential but is very useful as most Attribute Types will need SNMP. The main exeption being Reachability, TCP Ports and NTP.
As expected, Hosts have a management address, a name, optionally three `SNMP Communities`_ (read only, read/write and trap) plus some other parameters such as `Autodiscovery Policies`_. Hosts also belong to a single Zone.
Hosts do not have an User but may have a default User for Attributes found during Autodiscovery. This makes sense when a single Host may service many User’s services. For example, a common switch may have user A on port 1 and user B on port 2, or a particular server may have several websites owned by different users.
An Attribute is one of the major models that is used in RoseNMS. It is effectively something that you want to monitor or track within a Host. Attributes will have RRD values to update or a status to track or perhaps both these options.
The simplest idea of an Attribute is a physical interface. This Attribute Type has counters that turn into graphs such as an error or packet rate and the operational and administrative status that change the state of the Attribute. All other Attributes are variations of this idea, but follow the same basic concept.
Besides the Host it is bound to, an Attribute can have a SLA. The particular SLA that can be assigned to an Attribute is based upon the Attribute Type. The SLA uses the last 30 minutes of data to determine if the data are within some specification.
Attributes can have a poll priority. While it is not essential to set an Attribute for a host with a priority, it greatly helps with the efficiency of the poller.
Attributes with the poll priority are selected before normal Attributes. If Attributes within a host with poll priority set are down, then the remaining Attributes within that host are no polled. This means that with careful selection of prioritized Attributes, if an entire host is down then the poller doesn’t waste effort attempting to get to the host. The most common Attribute Type to assign for priority is Reachability. The idea being that if you cannot ping the host, then you cannot reach it and it doesn’t make sense to attempt to get any more data out of the device.
With a prioritized Attribute down for a Host, only the prioritized Attributes are polled.