From: Howard C. Berkowitz (hcb@xxxxxxxxxxxx)
Date: Fri Apr 19 2002 - 16:32:36 GMT-3
At 11:26 AM -0700 4/19/02, D. J. Jones wrote:
>Not sure why this was bounced.
> ----- Original Message -----
> From: D. J. Jones
> To: ccielab@groupstudy.com
> Sent: Friday, April 19, 2002 10:31 AM
> Subject: Multiple directed broadcasts
>
>
> I want to run a simulation that generates multipled directed broadcasts
>using UDP. I know
> I need to begin with the following config:
>
> interface fa0/0
> ip directed-broadcast
> ip helper-address xx.xx.xx.xx
> ip forward-protocol udp port
>
> I think this will forward directed broadcasts based on a specific udp port,
>but how would I have
> the router generate this traffic?
>
> thanks..dj
Several issues here, and it would help to have a better understanding
what you are trying to do. I can understand why you'd want directed
broadcast, and I can understand why you'd want helper addresses. I'm
less clear why you'd want to use them together. I've certainly used
directed broadcast to a subnet that contains multiple DHCP, DNS, and
TFTP servers...but the servers are on the subnet. They aren't on
another subnet to which you forward.
First, it's significantly more difficult to use a router both to
generate traffic and then act on it than it is to use a separate
router, or usually better a host, as traffic generator. That being
said, if the router hardware and software permitted, you might try
wrapping a cable from one interface to the FA0/0, and do some
interface-specific things such as having that interface ask for a
dynamic DHCP address.
I think the easiest thing would be to hook up a host and do DNS
queries as fast as possible, with the query going to the broadcast
address on the subnet.
Again when doing performance measurement (assuming that's what you're
trying to do), it's usually best to have a traffic generator and a
traffic receiver, with the router as a pass-through in the middle.
One of the reasons for this is the router may rate-limit* ICMP or
other management traffic directed to it, but won't do so for traffic
it is routing from interface to interface.
*It's not rate-limiting in the sense of CAR, but trying to respond in
the main processor, and you get into the amount of processing cycles
that will be allocated to this task.
-- "What Problem are you trying to solve?" ***send Cisco questions to the list, so all can benefit -- not directly to me*** ******************************************************************************* * Howard C. Berkowitz hcb@gettcomm.com Chief Technology Officer, GettLab/Gett Communications http://www.gettlabs.com Technical Director, CertificationZone.com http://www.certificationzone.com "retired" Certified Cisco Systems Instructor (CID) #93005
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