[CentOS] Monitoring Dynamic IPs using Some network monitoring tool

Tue Dec 22 13:37:24 UTC 2009
Les Mikesell <lesmikesell at gmail.com>

Rajagopal Swaminathan wrote:
> Alternatively, it there a possibility of installing some agent and
> getting the MAC address of one of the server behind the router. First
> a diagram
> central location (main monitoring -- Centos box0+monitoring server)
> |
> |
> (Internet)
> |
> |
> +--link1adsl-- Remote1 (dynamic IP)
> |
> |
> +--link2adsl-- Remote2 (dynamic IP)
> |
> (and so on...)
> In each remote I have a centos box behind the router serving a bunch
> of desktops.
> Is there a possibility that I can install an agent which will contact
> the central montoring server? (No $$$ here please, as free as in free
> beer/bread applies in addition to freedom)

Why not run Openvpn on the remote and central centos boxes to create a big 
private network, using unique IP ranges for each remote?  This can be used for 
other management purposes or could be firewalled to just permit snmp.  For what 
you describe, all you need is a route to the routers, and this would give you a 
route to the 'inside' interface.  If you want to allow it, it will also allow 
remote access to everything behind the router.

> BTW it seems there are two type of monitoring tools:
> Type-1. uses snmp only
> Type-2. user agents

Your router is probably only going to have snmp, and accessing it from the 
inside interface will work to report the interface usage of all interfaces.

> Is it possible to monitor a link based on the MAC of the centos server
> sitting behind?

Probably not, but you can vpn-tunnel through it, and openvpn will work fine 
through NAT and with one end having a dynamic address.

> Zabbix seems to be priced
> Honestly I am absolutely confused as to which I should choose as it
> will be maintained by people who may not know what command line is
> (Sorry!!)
> Apologies for too many questions.
> I think somebody mentioned NMS to be complex beasts .. I being a
> vegetarian am finding it all the more daunting

I'm partial to opennms - and have used it in somewhat similar circumstances 
(generally static IP's, but using a central monitor from the private side 
through tunnels). The one thing you need for this to work is unique IP addresses 
throughout, though.  Most monitor tools will be tied to IP addressing and will 
be confused if each location NATs to the same range.

   Les Mikesell
    lesmikesell at gmail.com