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Cisco Bug: CSCur02983 - VCS keeps tcp connections open longer than desired

Last Modified

Mar 19, 2020

Products (3)

  • Cisco TelePresence Video Communication Server (VCS)
  • Cisco TelePresence Video Communication Server Model
  • Cisco Expressway

Known Affected Releases

X7.2.3 X8.1.1

Description (partial)

The VCS will keep a TCP connection open and idle for over 2 hours before sending a FIN and closing the connection. This can cause firewalls to age out the connection and cause subsequent packets associated with this connection to be blocked.

When the VCS makes calls over the DNS zone the TCP connection is left open and idle for a longer than desired time. This is most prominent in Webex enabled telepresence deployments. When the VCS sets up a call to webex it will open up a new TCP connection. When the call ends and we start a new call to Webex the VCS can reuse the same port and will reuse the previous open and idle TCP connection. When it tries to do this it is possible for the firewall to have aged out the connection and the call attempt will be blocked because the firewall will see the packets as out of state.
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