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New Member

Port blocking without ACL's?

Hi, I am using a Cisco 3750 switch that connects to Avaya phones and an Avaya call server. The problem I am having is that port 1720 does not seem to be going through the switch. But I don't have any kind of access-list applied at all. Does anyone have any ideas as to why this is happening?


Re: Port blocking without ACL's?

Is it a simple topology e.g. the server and phones on the same VLAN? Can the server ping the phones? Use the switch's telnet client (with /source-interface) to try to open the socket on the server.

New Member

Re: Port blocking without ACL's?

Same VLAN, we can use telnet and ping. The only thing that does not work is port 1720.


Re: Port blocking without ACL's?

Then it sounds to me like the issue is your server. Are you sure there's not some host firewall on the thing?

TCP/1720 is H323 for the poster that asked.

New Member

Re: Port blocking without ACL's?

Hi - What is supposed to be listening on this port??

If everything is on the same VLAN then there shouldn't be a problem if what ever is listening on port 1720 is in fact set up correctly.

However, if the phones and call server are on a voice VLAN (which is usually the case) you may not be able to get to the other vlan at all.

Hope that helps,


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