This document provides information about the Session Initiation Protocol (SIP) Application Level Gateway (ALG), which is a customer-side firewall feature, and why it must be disabled to ensure the proper operation of Cisco WebEx

Symptoms
Some possible symptoms, which will vary depending on the environment and firewall type, are shown below:
Device registration to the service network fails.
Device cannot receive and/or place calls.
Calls connect as audio-only when calling other video devices.
Calls drop after several minutes.

If the device is not connected to a Redcentric network then it is the customers / users responsibility to disable SIP ALG. Redcentric is unable access personal routers/firewalls