We recently had a security scan which picked up that TCP Port 1999 was administratively prohibited. Further analysis indicated that an ACL on our ISP's router (Cisco 2500 on 11.3) is filtering any host communicating with the router on TCP Port 1999.
I am being asked to explain why this is and can find no reference on CCO other than:
http://www.cisco.com/univercd/cc/td/doc/product/iaabu/csids/csids1/nr221rn.htm
This URL returned the document "NetRanger Version 2.2.1 Release Notes".
This however, does not shed any light. The IANA listing of port numbers show this to be "Cisco-Indentification-Port".
Can anyone enlighten me as to what is listening on Port 1999, what is exchanged over this port and what the vulnerabilities are, that would cause our ISP to block this with an ACL.
