Ethereal-users: Re: [Ethereal-users] Monitoring Cisco Router using Ethereal

Note: This archive is from the project's previous web site, ethereal.com. This list is no longer active.

From: "Erick B." <erickbe@xxxxxxxxx>
Date: Fri, 13 Jul 2001 16:16:34 -0700 (PDT)
If you're to use Ethereal to receive and display SNMP
traps sent to the machine running Ethereal then that
isn't a function of Ethereal. If you are capturing
traffic with Ethereal then the SNMP traps should show
up in the captured packets (trace) if no filters are
being used.

If you want something to display the SNMP traps
received then you'll need a syslog/network mgmt/SNMP
trap program of some sort. 

--- Guy Harris <guy@xxxxxxxxxx> wrote:
> > 	I´m trying to capture snmp traps(linkdown) on a
> Cisco Router
> > (AS5800) using Ethereal.  Well, i configured the
> router but Ethereal
> > didnt get a thing.
> > 	Has anyone had experience with that? Is Ethereal
> capable of
> > capturing these traps?
> 
> Ethereal's *capable* of capturing any packet that it
> can get from the
> underlying packet capture mechanism.  There's
> nothing particularly
> special about SNMP traps.
> 
> However, if the trap wasn't sent to the machine that
> was running
> Ethereal (or tcpdump, or Network Associates'
> Sniffer, or Microsoft
> Network Monitor, or KSnuffle, or...), the packet can
> be captured by the
> underlying packet capture mechanism only if
> 
> 	the packet is sent on a network the machine running
> the packet
> 	capture program is on;
> 
> 	the network isn't switched (i.e., the machine
> running the packet
> 	capture program isn't plugged into a switch or
> switching hub),
> 	or the port into which that machine is plugged is
> set up to see
> 	all traffic on the switched network (some switches
> let you do
> 	that; how it's done depends on the switch, and I
> don't know the
> 	details of how to do that for any switch);
> 
> 	the capture program is configured to put the
> network interface
> 	into promiscuous mode (note that promiscuous-mode
> captures may
> 	not work with Ethereal 0.8.18 if you're running in
> "Update list
> 	of packets in real time" mode; there is a
> workaround, but you'd
> 	probably be better off just getting the
> recently-released 0.8.19
> 	release, which fixes that bug);
> 
> 	the network interface's driver supports promiscuous
> mode;
> 
> 	the network interface itself supports promiscuous
> mode.
> 
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>
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