Blocked router in host list

[Marc Powell]

> -----Original Message-----
> From: Bas Rijniersce [mailto:bas at brijn.nu]
> Sent: Thursday, September 19, 2002 10:22 AM
> To: Marc Powell; nagios-users at lists.sourceforge.net
> Subject: Re: [Nagios-users] Blocked router in host list

> 
> THat's a good idea. I'm not yet very familair with the way the plugins
are
> setup. And also i'm not fully aware why a traceroute is showing the
host,
> while a ping is not (but my network book will show me :).. Using the
> output
> is a simple and effective way (if you work around timeout problems)


Take a look at check_sensors... It's fairly simple and straightforward
and could easily be modified to do the traceroute check.

Traceroute and ping utilize two different types of ICMP packets. From
the traceroute man page "Traceroute utilizes the  IP  protocol  `time
to  live'  field  and attempts to elicit an ICMP TIME_EXCEEDED response
from each gateway along the path to some host." For security reasons,
ping is typically blocked to prevent ping floods etc... Since there are
no known DOS attacts related to single packet ICMP requests, they're
typically allowed as they're very useful in troubleshooting.

Marc


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