Monitoring Redundant path routers

[Peter Gutmann]

Well the answer to you question is that it depends. If you are using a 
routing protocol (i.e. rip, ospf) then your network should be able to 
withstand a single link failure (because an SNMP trap is just a network 
packet :-). The routing protocol will manage the traffic between Router1 
and Router3 and well as the traffic between Router2 and Router3. It's 
these three routers that should decide how to forward the traffic from the 
networks on the other side of the switch. So, if the interface or the link 
on Router 2 (192.168.0.5) fails, two things should happen
1) Router2 should send an SNMP trap saying "I have lost my connection to 
Router3 via 192.168.0.5"
2) Router3 should send an SNMP trap saying "I have lost my connection to 
Router2 via 192.168.0.6"
3) You may get a message from Router2 saying recalculating routes for 
192.168.2.0

Nagios will not see that the whole router is down (you should be using 
SNMP to check CPU and other "internal" values. It's the interface service 
that will fail....

Good luck
 
----
Peter Gutmann
Peter.Gutmann at db.com





"Samuel Petreski" <petreski at ksu.edu>
04/26/2004 02:22 PM
Please respond to petreski

 
        To:     Peter Gutmann/NewYork/DBNA/DeuBa at DBNA
        cc:     <nagios-users at lists.sourceforge.net>, 
<nagios-users-admin at lists.sourceforge.net>
        Subject:        RE: [Nagios-users] Monitoring Redundant path routers


Peter,
 
Thank you very much for replying to my post. I thought of using SNMP traps 
in order to be able to accomplish this, but what if the interface of the 
Router goes down to which I send the SNMP traps? Nagios than is going to 
think that the whole Router is down, which is not correct. 
 
If I send traps to Interface 192.168.0.10 on Router 3, and that interface 
is down, the router is not necessarily down, only the that interface.
 
--Samuel
 
-----Original Message-----
From: Peter Gutmann [mailto:peter.gutmann at db.com]
Sent: Monday, April 26, 2004 1:12 PM
To: Spencer Horn <shorn
Cc: nagios-users at lists.sourceforge.net; 
nagios-users-admin at lists.sourceforge.net; petreski at ksu.edu
Subject: Re: [Nagios-users] Monitoring Redundant path routers
 
Why can't you use SNMP for this? The line up and the line down events
should generate SNMP traps. At the very least, could you use SNMP mib to
poll the status of the device....

----
Peter Gutmann
Peter.Gutmann at db.com
-----Original Message-----
From: nagios-users-admin at lists.sourceforge.net 
[mailto:nagios-users-admin at lists.sourceforge.net]On Behalf Of Samuel Petreski
Sent: Monday, April 26, 2004 12:33 PM
To: nagios-users at lists.sourceforge.net
Subject: [Nagios-users] Monitoring Redundant path routers
 
Hi,
 
I was looking into using Nagios for Enterprise wide monitoring and am very 
impressed with all the capabilities, but ran into following question:
 
                                      192.168.0.1          192.168.0.2     
                       192.168.1.21
                        -------------------- 
--------------------192.168.1.1           --------------------
                        | Router 1     |----------------------------| 
Router 2     |----------------------------|  Nagios       |
                        -------------------- --------------------    
--------------------
                  192.168.0.9 \    /  192.168.0.5
                                     \        /
                                      \      /
                                       \    /
                                        \  /
                                         \ /
                                          \                             /
                                           \                          /
                                            \                       /
                                             \                    /
                                              \                 /
                            192.168.0.10\               / 192.168.0.6
                                              --------------------
                                              | Router 3     |
                                              --------------------
                                                      |  192.168.2.1
                                                      |
                                                      |  192.168.2.2
                                                -------------
                                                | Switch1|
                                                -------------
 
Can Nagios monitor the individual interfaces between the routers in order 
to inform me when a link/interface goes down? I'm mainly interested if 
monitoring Router 3, to have Router 1 and Router 2 as dependencies, but 
also to know if the link between Router 1 and Router 2 goes down, because 
Nagios will be able to reach Router 3 through the link between Router 2 
and Router 3.
 
Any help would be greatly appreciated and if further information is 
required, please feel free to let me know.
 
--Samuel
 
P.S. If this is a cross post, please let me know where I can find the 
original post.




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