Cisco TelePresence Administrator's Manual page 232

Note that you must create a separate traversal server zone for every system that is its traversal client.
Configuring other traversal server features
For the VCS Expressway to act as a firewall traversal server for traversal-enabled endpoints (such as
n
Cisco MXP endpoints and any other endpoints that support the ITU H.460.18 and H.460.19 standards), no
additional configuration is required. See
for more information.
To enable TURN relay services and find out more about ICE, see
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To reconfigure the default ports used by the VCS Expressway, see
n
Firewall traversal and Dual Network Interfaces
The Dual Network Interfaces option key enables the LAN 2 interface on your VCS Expressway (the option is
not available on a VCS Control). The LAN 2 interface is used in situations where your VCS Expressway is
located in a DMZ that consists of two separate networks - an inner DMZ and an outer DMZ - and your
network is configured to prevent direct communication between the two.
With the LAN 2 interface enabled, you can configure the VCS with two separate IP addresses, one for each
network in the DMZ. Your VCS then acts as a proxy server between the two networks, allowing calls to pass
between the internal and outer firewalls that make up your DMZ.
Note: all ports configured on the VCS, including those relating to firewall traversal, apply to both IP
addresses; it is not possible to configure these ports separately for each IP address.
Cisco VCS Administrator Guide (X7.2)
Configuring Expressway and traversal endpoint communications
Firewall traversal
About ICE and TURN services.
Configuring traversal server
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ports.