3750 Cisco Switch

Unanswered Question
Apr 1st, 2009


Is it possible to open two UDP ports on this switch (1194 or 2114) ? I found that TCP and UDP are enabled for all ports by default, but it seems that I still must configure something on a per-port-basis. Please advise if you have any knowledge.


I have this problem too.
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Jon Marshall Wed, 04/01/2009 - 14:11


Not sure what you meab. Unless you have configured acl's all ports are allowed through both switches and routers.

Perhaps you could clarify ? Are these destination broadcast addresses you are referring to ?


pcgajewicz Wed, 04/01/2009 - 14:25

We have no ACL's. So...you are saying that all UDP and TCP traffic is allowed through each port unless specified by a ACL?

We are basically trying to get traffic through our 3750G-24PS switch from one vendor and that vendor is saying that they have created their UDP traffic using Ports 1194 and 2114. They are seeing the traffic drop when it comes to our switch. Do you know if there is anything I need to configure to allow this traffic?

Jon Marshall Wed, 04/01/2009 - 14:28

If the traffic is unicast ie. from a specific src IP address/src port to a specific destination IP address/dst port then your switch should not be dropping this traffic.

Is your 3750 acting as a L2 or a L3 switch ?


pcgajewicz Wed, 04/01/2009 - 14:34

I guess the vendor wants us to setup a router and then a seperate 3750 switch then. Maybe its b/c I don't have this switch as a L3 switch.

Jon Marshall Wed, 04/01/2009 - 14:37


Shouldn't matter if the switch is L2. It will forward unicast/multicast/broadcast.

Does the vendor specify how they know this switch is the issue. Do you have any sort of broadcast/multicast/unicast storm control configured on the ports ?


pcgajewicz Wed, 04/01/2009 - 14:44

No no storm control configured.. This is kinda 3rd party info. They are now alluding that if we could get a router out and switch to configure this.

Jon Marshall Wed, 04/01/2009 - 14:51

You need more specifics from them. Rather than them dictate what they want you need to understand why they think a router would fix the problem.

They may have a valid reason but from the info you have posted so far it is not clear.


lamav Wed, 04/01/2009 - 15:00


As Jon stated, it's an L2 switch, man...like who cares what UDP port they're using, dude...like you have an L2 switch that passes all kinds of good traffic - unicast, multicast, broadcast...

All the switch is doing is looking at the MAC addresses, man, so it can forward them. Unless you got QoS/CoS or some other service configured on that L2 box that does deep packet inspection, the switch only cares about MACs...

Give us a diagram if you have one...


pcgajewicz Thu, 04/02/2009 - 07:15

No, I've got it. What we need to do has been defined better this morning. We are going to need a router and a switch in our case. Thanks guys.

hobbe Thu, 04/02/2009 - 07:20

This sounds like they have a problem with something and they can not handle it.

Most likely there is something else going on.

1st the 3750 can be used as a router so that argument falls there.

2nd if what is told above is true then the switch should work straight of the shelf.

are you shure you do not have any access-lists installed in the switch ?

are there any configuration at all ?

You want the answers to the questions

1) what type of packet are they trying to get through the system?

ie unicast udp port 1234

2) how do they know that the packet is beeing dropped in the switch ?

ie what proof do they have ?

3) how do they think a router would make this work ? what are their arguments for that ?

and if you could just make a network overview on what they are trying to do.

good luck

Leo Laohoo Thu, 04/02/2009 - 14:30

Do you want to shed some light as the the "product" your organization is testing out? There's alot of regulars here who has extensive experience and may know how to resolve.

carl.wertz Fri, 04/03/2009 - 12:14

Are you forwarding those messages on those ports...

ip formward-protocol udp | tcp "port number"


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