Router has many interfaces(and ip's) what will be the parent?

[Greg Vickers]

matato at pregi.net wrote:
> Hi,
>   I'm currently monitoring servers of two different networks.
> 
> 202.90.158.x and
> 202.90.128.x
> 
> Nagios works fine alerting me when the host goes down or up, but the
> entries for hosts.cfg doesn't include a "parent"(I have commented it.)

If you don't use the parent directive, consider the following situation:
Say you are monitoring 100 hosts on the 128 subnet and the 128 Switch 
goes down. If you don't have the 128 Switch set as the parent of all the 
subnet 128 hosts you will receive 100 notifications instead of ONE.

> Upon further readings of the documentation, I've came across the
> monitoring remote hosts. I've found out that alert for host status can
> either be DOWN or UNREACHEABLE if I put something in the "parent" section
> right?
> The network setup with those two subnets above looks like this:
> 
> 
>                ISP
>                 |
>                 |
>              Router
>              ||||||
>             /      \
>            /        \
>     158 Switch   128 Switch
>          /            \
>         /              \
>  nagios,server1,2     server3,server4
> 
> As you can see, the router has many interfaces. Nagios belongs to 158
> network. I'm monitoring servers 1,2,3,4 both from different networks. I
> have tracerouted from my nagios server to a 128 server(server4) and found
> out that 202.90.158.1 is the ip of the interface in the router where
> nagios is passing to get to the 128 servers.
> Questions:
> What will be the parent for a 128 server?

The 128 Switch

> Is it the 202.90.158.1 or is it the ip of the interface in the router
> where 128 block passes to get through 158 block if I am to do a traceroute
> this time from a 128 machine to a 158 machine?

Any traffic from Nagios goes to the 158 Switch then to the 158 interface 
on the router then out the 128 interface on the router then to the 128 
Switch then on to the host in question. So the traceroute passes through 
both of these interfaces.

> And if I already know what the parent should be, do I have to create
> additional hosts.cfg entry for this host? Will it have a parent two?

Yes you do have to create more hosts:

server4, parent '128 Switch'
server3, parent '128 Switch'
128 Switch, parent 128routerinterface
128routerinterface, parent 158routerinterface
158routerinterface, parent '158 Switch'
(depending on how much you want to monitor, you could make one router 
host and create several services on that host to check each interface)
server1, parent '158 Switch'
'158 Switch', parent nagiosserver

With the above hosts and parent directives you will get a pretty 
network-like layout in your Nagios maps (rather than a heap of hosts all 
clustered around the nagios process...) and if a Switch or router 
interface goes down you will only receive one notification, and not for 
all the servers on the 158 subnet.

GL,
-- 
Greg Vickers
Lab Monitor Project Manager
Teaching and Learning Support Services
Information Technology Services
Queensland University of Technology

email: g.vickers at qut.edu.au
phone: (07) 3864 8276
mobile: 0416 001 674, SD #6 6147

CIROS code: 00213J


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