Nagios

On Thu, 2004-08-26 at 10:24 -0500, Marc Powell wrote:

> This is standard routing, controlled by your OS. All checks will go out
> the interface specified as your default route unless you have more
> specific routes set up. All programs have very little control over how
> their outbound traffic is routed. If they did, they would have to be
> aware of the state of the network to avoid routing deficiencies...

Not entirely true.  ping(1) has an option to specify the source
interface.  It would not surprise me if it required root privs to do so.

Wil
--=20
Wil Cooley                                 wcooley@...
Naked Ape Consulting                        http://nakedape.cc

There is a way you can accomplish what i think your trying to accomplish 
using iproute2, although there is a catch
You can route all local traffic out any interface (virtual or otherwise) 
you want with a routing rule and a secondary routing table
The catch is that if the interface goes down (layer two, or 
administratively) than the secondary routing table is lost (although 
there is a set of patches you can install that will mitigate this 
problem, see "http://www.ssi.bg/~ja/" and the dead gateway 
detection/static routes patches)


---
#!/bin/bash
NETWORK=192.168.100.0
VINT_IP=192.168.100.80
ETH2_GW=192.168.100.254

 ip rule pref 10000 dev lo table 400
 ip route add $NETWORK src $VINT_IP dev eth2 table 400
 ip route add default via $ETH#_GW dev eth2 table 400

----

Where:
$NETWORK = The network address of the ip range, ie the network address 
of 192.168.100.0/23 is "192.168.100.0"
$VINT_IP = The ip address of the virtual interface
eth# = the interface, not the virtual interface
$ETH#_GW = the router for the virtual interfaces address range

this will route all locally generated traffic out the virtual interface 
(or at least using the virtual ip)
note: the system will still respond to requests using the default route 
if you have one installed, but there is other fun stuff you can do with 
responses to requests as well

its highely recommended you read the Linux Advanced Routing howto. At 
time ip routing with linux can become pretty arcane: http://lartc.org/


Marc Powell wrote:

>  
>
>>-----Original Message-----
>>From: Albert Spruyt [mailto:appie@...]
>>Sent: Thursday, August 26, 2004 3:17 AM
>>To: nagios-devel@...
>>Subject: [Nagios-devel] running checks on a specific network interface
>>
>>we are currently changing nagios servers (machine and nagios version).
>>The new machine has 2 network interfaces  as well as 3 virtual ones.
>>Is there an easy ( or a not so easy one) way to get the traffic from
>>    
>>
>the
>  
>
>>nagios checks onto a specific network interface?(like the apache
>>listen:*.*.*.*:** directive) If no-one  seems interested please point
>>    
>>
>me
>  
>
>>in the right direction. could it be done with  a wrapper script?
>>or would it mean changing all the checks? or has it already been
>>implemented?
>>it would allow me in the future to change nagios to a diffrent server
>>whithout much hassle.
>>( we like our servers that way ;) )
>>    
>>
>
>
>This is standard routing, controlled by your OS. All checks will go out
>the interface specified as your default route unless you have more
>specific routes set up. All programs have very little control over how
>their outbound traffic is routed. If they did, they would have to be
>aware of the state of the network to avoid routing deficiencies...
>
>--
>Marc
>
>
>
>
>
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>  
>

Wil Cooley wrote:
> On Thu, 2004-08-26 at 10:24 -0500, Marc Powell wrote:
> 
> 
>>This is standard routing, controlled by your OS. All checks will go out
>>the interface specified as your default route unless you have more
>>specific routes set up. All programs have very little control over how
>>their outbound traffic is routed. If they did, they would have to be
>>aware of the state of the network to avoid routing deficiencies...
> 
> 
> Not entirely true.  ping(1) has an option to specify the source
> interface.  It would not surprise me if it required root privs to do so.
> 

ping is installed suid root on most (all?) linux systems, since it also 
requires root access to open raw sockets and send ICMP packages. That 
doesn't really matter, however, since the interface's routing table also 
needs to match the destination IP, and what good would it do to have two 
different interfaces in the same subnet that aren't bonded?

> Wil

-- 
Andreas Ericsson                   andreas.ericsson@...
OP5 AB                             http://www.op5.se
Lead Developer

On Fri, 2004-08-27 at 07:26 +0200, Andreas Ericsson wrote:

> ping is installed suid root on most (all?) linux systems, since it also=20
> requires root access to open raw sockets and send ICMP packages. That=20
> doesn't really matter, however, since the interface's routing table also=20
> needs to match the destination IP, and what good would it do to have two=20
> different interfaces in the same subnet that aren't bonded?

Yes, but setting the interface also affects the source IP address, which
is where I've used it--for example, testing IPSEC tunnels.  I cannot say
why the original posted wanted the feature; the answer from several of
you was "that's not theorectically possible to do in the program itself;
use routing tables" and my response was that it is in fact possible.
Practical or easy, I do not know.

Wil
--=20
Wil Cooley                                 wcooley@...
Naked Ape Consulting                        http://nakedape.cc

Wil Cooley wrote:
> On Fri, 2004-08-27 at 07:26 +0200, Andreas Ericsson wrote:
> 
>>ping is installed suid root on most (all?) linux systems, since it also 
>>requires root access to open raw sockets and send ICMP packages. That 
>>doesn't really matter, however, since the interface's routing table also 
>>needs to match the destination IP, and what good would it do to have two 
>>different interfaces in the same subnet that aren't bonded?
> 
> 
> Yes, but setting the interface also affects the source IP address, which
> is where I've used it--for example, testing IPSEC tunnels.  I cannot say
> why the original posted wanted the feature; the answer from several of
> you was "that's not theorectically possible to do in the program itself;
> use routing tables" and my response was that it is in fact possible.
> Practical or easy, I do not know.
> 

This is news to me, unless you're talking about measuring on the 
interfaces themselves (throughput, status and so on) and not actually 
picking an interface to send traffic from and receive responses to while 
the kernel has a different opinion on what the best route would be. Can 
you give us a couple of examples, maybe?

> Wil

-- 
Andreas Ericsson                   andreas.ericsson@...
OP5 AB                             http://www.op5.se
Lead Developer