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New Member

UDP via 3750 Switch

I am trying to send a UDP socket stream from a client to a server on a LAN. A 3750 switch stack sits in the middle. The udp packets appear to be getting to the switch but are not being forwarded to the server (fixed ip address and specific port). If I go via a different make of switch everything works fine so I guess I need to get something configured on the 3750. Is there anyway of allowing UPD traffic through?



Hall of Fame Super Blue

MarkUDP traffic is not


UDP traffic is not normally blocked by any switch ie. it is just IP traffic which is forwarded by default.

So -

1) are you talking about UDP unicast traffic ?

2) do you have any acls configured anywhere ?

3) what is the stack doing ie. it is just L2 or is it L3 and doing routing between vlans ?

Perhaps if you could provide some more details we may be able to help.


New Member

Thank you for your reply Jon.

Thank you for your reply Jon.


1) It is unicast traffic. The client is an ASP.NET application sending a stream to a serial convertor that has a fixed IP address and listens on a specific port.

2) Not sure about the ACL's, I'll confirm this tomorrow morning when I'm back at work.

3) It's a layer 3 stack and there is routing between vlans.


As mentioned previously, if I route the traffic via a HP switch everything works ok so I'm farily sure the cisco config needs tweaked??




New Member

As per above, the are no ACLs

As per above, the are no ACLs configured.

Still struggling with this if anyone has any ideas. The switch is definitley stopping the udp stream but not sure why?


Hall of Fame Super Blue

MarkCan you post the config


Can you post the config of the switch +

1) what is the source IP

2) what is the destination IP


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