Dual-port monitoring

[Israel Brewster]

On Mar 17, 2008, at 12:00 PM, Marcel wrote:

> If you would have a round-robin dns setup to reach that particular  
> host, you would be fine tweaking a check_host_alive command with  
> high lost percentage, but still reachable. But you will rely on dns  
> name resolution to do that.

Right, unfortunately we aren't set up quite that fancy. We simply have  
two seperate DNS entries for the two ports, and when we can't reach  
the device on  one, we go on the other. The dual connections are more  
for outgoing traffic than incoming, such that devices behind the  
device will still have a route to the outside world should one route  
die (load balancing and failover), but nagios is on the outside  
looking in.

-----------------------------------------------
Israel Brewster
Computer Support Technician
Frontier Flying Service Inc.
5245 Airport Industrial Rd
Fairbanks, AK 99709
(907) 450-7250 x293
-----------------------------------------------
>
>
> HTH,
> Marcel
>
> On Mon, Mar 17, 2008 at 4:45 PM, Israel Brewster <israel at frontierflying.com 
> > wrote:
> On Mar 17, 2008, at 11:03 AM, Cook, Garry wrote:
>
>> Do you have the ability to use loopback addresses on these devices?  
>> If so, that would be used as the host address, and then you could  
>> use other checks for the interfaces. For instance, all of my Cisco  
>> routers have a loopback setup. I then use 'check_ifstatus' to check  
>> the individual interfaces.
>>
>> Thanks,
>> Garry
>>
>
> I assume the check_ifstatus for the interfaces are services  
> associated with the host? If so, then what do you use for your host  
> check? How do you get the host to show as down if all the interfaces  
> are down, but not if one or both (or more, if you have more than  
> two, although that is not the case with any of our devices) are up?
>
> -----------------------------------------------
> Israel Brewster
> Computer Support Technician
> Frontier Flying Service Inc.
> 5245 Airport Industrial Rd
> Fairbanks, AK 99709
> (907) 450-7250 x293
> -----------------------------------------------
>
>> From: nagios-users-bounces at lists.sourceforge.net [mailto:nagios-users-bounces at lists.sourceforge.net 
>> ] On Behalf Of Israel Brewster
>> Sent: Monday, March 17, 2008 12:41 PM
>> To: Nagios Users Mailinglist
>> Subject: Re: [Nagios-users] Dual-port monitoring
>>
>> On Mar 17, 2008, at 9:03 AM, Gary Every wrote:
>>
>>
>> In your services file:
>>
>> define service {
>>   use                   generic-service
>>   name                  Ping
>>   host_name        multi_homed_server_name
>>   service_description   Ping Second IFace
>>   check_command         check_ping2!10.1.1.100!3000,10%!10000,20%
>>   contact_groups        Unix
>> }
>>
>> for your checkcommands:
>>
>> define command{
>>         command_name    check_ping2
>>         command_line    /usr/lib/nagios/plugins/check_ping -H  
>> $ARG1$ -w $ARG2$ -c $ARG3$ -p 5
>>         }
>>
>>
>> check_ping2 adds the first ARG as the ip address that you want  
>> monitored - This means that the HOSTNAME will remain the same, but  
>> a diff interface will be checked.
>>
>>
>> Thanks for the response. If I understand your reply correctly,  
>> though, this just adds a second service for the host, with a  
>> separate IP from that specified in the host directive. it does not,  
>> however, allow me to monitor the HOST on two separate IP's, taking  
>> into account that if either interface is up, the host is up.  
>> Perhaps my question wasn't quite clear enough. Take, for example,  
>> the following situation:
>>
>> host a has two network interfaces: a primary with an IP of  
>> 10.1.1.100 and a secondary with an IP of 10.1.1.101.
>> Host a can be reached through either interface.
>> Host a has its host address defined as the primary of 10.1.1.100,  
>> with a check command of check_ping
>> Host a also has a service defined as above, checking the secondary  
>> interface (10.1.1.101)
>>
>> If the secondary interface goes down, then everything is fine:  
>> nagios notices that the service for the secondary interface is  
>> critical, checks the host on the primary, sees that as being fine,  
>> and sends an alert about the service (secondary port), while  
>> leaving the host in an OK state. This is exactly as it should be.
>>
>> However, now imagine that the primary interface goes down instead.  
>> Nagios attempts to check the host on the primary interface, which  
>> also fails (sicne the interface is down), and therefore nagios  
>> alerts that the host is down, and any devices behind it are  
>> unreachable. This, however, is incorrect-since the secondary  
>> interface is still connected and fully functional, the host and  
>> everything behind it is still up and reachable. What I want is a  
>> situation where Nagios will send me an alert if either interface of  
>> a host is down, but only consider the host to be down if BOTH  
>> interfaces on the host are down. As I explained in my original  
>> posting, I have considered a couple of options that may accomplish  
>> this, but neither seems as elegant as I would like. Thanks for any  
>> thoughts!
>>
>> -----------------------------------------------
>> Israel Brewster
>> Computer Support Technician
>> Frontier Flying Service Inc.
>> 5245 Airport Industrial Rd
>> Fairbanks, AK 99709
>> (907) 450-7250 x293
>> -----------------------------------------------
>>
>> On Mon, Mar 17, 2008 at 9:38 AM, Israel Brewster <israel at frontierflying.com 
>> > wrote:
>> I have a number of devices on my network that have dual-interfaces
>> such that either one can go down, but the device itself, and all the
>> devices behind it (in the case of a router) is still up and  
>> reachable.
>> What is the best way to set up monitoring of such devices,  
>> considering
>> that as far as I can tell you can only assign one IP per host? I have
>> looked at check_cluster, but if that is the best method I am unsure  
>> of
>> the best way of implementing it. Things I have thought of:
>>
>> 1) Create two "dummy" hosts which are the two ports, and then a third
>> host with a check command of check_cluster that looks at those two
>> dummy hosts. This seems overly complicated, not to mention cluttering
>> up my configs and nagios interface with three hosts where there is
>> really only one.
>>
>> 2) Simply monitor the two ports as two separate hosts. This could
>> work, but again clutters things up with multiple hosts where only one
>> exists, and adds the requirement of multi-parenting any child  
>> devices,
>> which can get ugly, especially in a graphical representation of the
>> network.
>>
>> I have read http://nagios.sourceforge.net/docs/2_0/clusters.html, but
>> that doesn't seem to apply, at least not directly, in that it refers
>> either to situations where you have redundant services on one or more
>> hosts (perhaps that is sort of what I want?) or to where you have
>> multiple redundant hosts, but not to the situation where you have one
>> host offering one service over two ports. The main problem with that
>> doc, though, is that the cluster is always a service, which wouldn't
>> work in my situation, as the host itself is a cluster. Any thoughts?
>> Thanks.
>> -----------------------------------------------
>> Israel Brewster
>> Computer Support Technician
>> Frontier Flying Service Inc.
>> 5245 Airport Industrial Rd
>> Fairbanks, AK 99709
>> (907) 450-7250 x293
>> -----------------------------------------------
>>
>>
>>
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>>
>>
>> -- 
>> Gary Every
>> "Pay it Forward!"
>>
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