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New Member

UDP setting on Catalyst?

Hi there.

I am annoyed cause of a problem i got lately...

Here's what it is all about:

I have two hardware gadgets which do something like serial over

ethernet, anyway this is not the point. They work in pairs. Each one

has an IP address hardcoded into its ROM or whatever they got in there..

They also have an entire IP stack and are capable of serving ftp, http

and maybe more.. They work like this: given the fact that they have

addresses in the same (sub)network, i.e., the two devices

in the mentioned pair communicate over ethernet and do their job. I can

even ping them when i'm on the same net. All traffic between the two

guys when they communicate with each other is UDP.

So i first tried a crossover patch cord. It worked great.

Same with a ethernet hub. Perfect!

And now i tried to integrate them in my network. It's a full-switched

ethernet, built around a 7200 router and a dozen Catalysts (2900XL and

3500XL). Well, it didn't work at all as expected or as it worked when

the devices were linked together with a crossover cable or with a hub!!!

From the tests i've been conducting for the last 2 days, i can only


one conclusion: the two devices experience dramatic packet loss when

talking UDP only if they are connected with a Catalyst switch. If they

are in the switch i can however ping them without a single packet

lost. I didn't try any other switch for the simple fact that i don't

have one. All i have is this bunch of Catalyst switches.

So, what could be wrong on the switch? Anyone ever bumped into such kind

of problems? Please please help me. I can't seem to find the setting

responsible for this problem (if any).

Please forgive the length of this post. I really hope some of you

guys will read it and understand what it says.

Any and all responses much appreciated .


New Member

Re: UDP setting on Catalyst?

Switches are layer 2 aware only, It doesn't matter if the packet is tcp or udp.

1. Are the packets created by these devices unicast or broadcast ?

2. If you put both devices on the same switch, what happens ?

3. If you put devices on different switches, and route between, what happens ?

What port settings do you have for the two devices ?

i.e. is portfast on....

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