IP Communicator 7.0.6

Answered Question
Mar 19th, 2012
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I am trying to get a users IP communicator to work but our firewalls guys are seeing our TFTP server getting blocked when it tries talking back on UDP port 1545. Does anyone know why it would be using this UDP port? I haven't found anything on the cisco site referencing this port and our firewall guys will not allow this port unless there is some documentation as to why.

Correct Answer by Aaron Harrison about 5 years 5 months ago

Hi


TFTP uses random ports.  From http://en.wikipedia.org/wiki/Trivial_File_Transfer_Protocol:


... Data transfer is initiated on port 69, but the data transfer ports are chosen independently by the sender and receiver during initialization of the connection. The ports are chosen at random according to the parameters of the networking stack, typically from the range of Ephemeral ports.


Aaron

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Correct Answer
Aaron Harrison Mon, 03/19/2012 - 10:08
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Hi


TFTP uses random ports.  From http://en.wikipedia.org/wiki/Trivial_File_Transfer_Protocol:


... Data transfer is initiated on port 69, but the data transfer ports are chosen independently by the sender and receiver during initialization of the connection. The ports are chosen at random according to the parameters of the networking stack, typically from the range of Ephemeral ports.


Aaron

Aaron has it (+5). Generally configuring application inspection on your firewall for the TFTP protocol (called a service policy on an ASA, other firewalls call it different things) will generally cause the firewall to automatically open the correct inbound ports.


HTH. Barry


Barry Hesk

Intrinsic Network Solutions

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