host_port objects - Enhancement Request

[Jason Frisvold]

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Greetings,

	We are planning on submitting an enhancement request to Nagios with the
intention of having their professional services group code this for us.
 We are interested in having our changes made available to the community
as well, so we wanted to get feedback from the community before we
submit the proposal.  Any and all feedback is welcome.

Thanks.

	
Nagios Enhancement Proposal

Overview

Currently, there are two primary ways to add individual physical ports
for a port-based device.  Each method has both advantages and
disadvantages, but neither fully satisfies the needs of Lafayette and,
likely, other institutions.

Service-based Ports

The first method is to treat ports as a service of a host and add them
as service entries.  The following configuration snippet demonstrates this :

define host {
   use                  cisco-switch-standard
   host_name            switch.lafayette.edu
   address              192.168.0.100
   hostgroups           cisco-switch-standard
   parents              router.lafayette.edu
}

define service {
   use                  service-standard
   hosts                switch.lafayette.edu
   servicegroups        cisco-switch-standard
   service_description  Switch Port Gi1/0/1
   check_command        check_snmp_traffic!-N Gi1/0/1!-C $USER2$
}

In short, this configuration defines a host and then a service for that
host which is, essentially, an snmp check that monitors the traffic on a
specific port.

Advantages
* Cleanly links a port to a switch
* Somewhat easy to add/remove specific hosts that need that port monitored

Disadvantages
* Parent/child relationships are difficult, if not impossible, to define
* Making service changes for a single port requires creating a unique
new service
* Service descriptions can get a bit long when they need to have a
meaningful description associated with them
* Ports with associated addresses are more difficult to define


Host-based Ports

Another method to accomplish this is to create a “fake” host entry for
each port and then assign services to those ports for monitoring.  The
following configuration snippet demonstrates this :

define host {
   use                  cisco-switch-standard
   host_name            switch.lafayette.edu
   address              192.168.0.100
   hostgroups           cisco-switch-standard
   parents              router.lafayette.edu
}

define host {
   use                  cisco-switch-standard
   host_name            switch-g1-0-1.lafayette.edu
   address              192.168.0.100
   hostgroups           cisco-switch-standard
   _PORT                Gi1/0/1
   parents              switch.lafayette.edu
}

define service {
   use                  service-standard
   hosts                switch.lafayette.edu
   servicegroups        cisco-switch-standard
   service_description  Port Traffic
   check_command        check_snmp_traffic!-N $_HOSTPORT$!-C $USER2$
}

This configuration defines two hosts, a switch and a port on that
switch, and then a service linked to the port.

Advantages
* Parent/child relationships work as expected
* A single service entry can be used for many port entries
* Very easy to deal with address-assigned ports such as router interfaces

Disadvantages
* Every port on every switch has to be defined
* Port host_name entries are often fake
* Port address entries are often duplicated


Proposed Solution

host-port object

define host {
   use                  cisco-switch-standard
   host_name            switch.lafayette.edu
   address              192.168.0.100
   hostgroups           cisco-switch-standard
   parents              router.lafayette.edu
}

define host_port {
   use                  cisco-switch-standard
   host                 switch.lafayette.edu
   port_name            Gi1/0/1
}

define service {
   use                  service-standard
   host                 switch.lafayette.edu
   port_based           true
   servicegroups        cisco-switch-standard
   service_description  Port Traffic
   check_command	check_snmp_traffic!-N $PORTNAME$!-C $USER2$
}

In this proposed configuration, a host is defined, as normal.  A new
object, the host_port object, is defined with port-based information.
The host_port object imports information such as address and host_name
from the host but can override this information if needed.  For
instance, a router interface may have an ip address and hostname.
Finally, a new tag, port_name, identifies the port name to use.  When
displaying the host_port in the GUI, or identifying it in email/SMS, the
port_name should be appended to the host_name.  A similar syntax could
be used for parent/child relationships as well.

The service definition uses a new tag, port_based, to identify that this
service is for the ports of a host, not for the host itself.  This
service should be applied to all ports.  port_name can be used in a
manner similar to host or hostgroups to restrict the service to specific
ports.

Advantages
* Clearly links ports to hosts
* Parent/child relationships can be clearly defined
* A single service entry can be used for many port entries
* Very easy to deal with address-assigned ports such as router interfaces

Disadvantages
* Every port has to be defined
* Concatenated host/port names can get a bit long

- -- 
- ---------------------------
Jason Frisvold
Network Engineer
frisvolj at lafayette.edu
- ---------------------------
"What I cannot create, I do not understand"
   - Richard Feynman
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