Cisco Cisco TelePresence Video Communication Server Expressway

Introduction 

The internal network elements are devices which are hosted on the organization’s local area network. 

Note: Elements on the internal network have an internal network domain name. This internal network 
domain name is not resolvable by a public DNS. 

For example, the Cisco VCS Control is configured with an internally resolvable name of 
vcsc.internal-domain.net (which resolves to an IP address of 10.0.0.2 by the internal DNS servers). 

The Cisco VCS Control is a SIP Registrar & Proxy and H.323 Gatekeeper for devices which are 
located on the internal network. 

The Cisco VCS Control is configured with a traversal client zone to communicate with the Cisco VCS 
Expressway in order to allow inbound and outbound calls to traverse the NAT device. 

These are example endpoints hosted on the internal network which register to the Cisco VCS Control. 

DNS servers used by the Cisco VCS Control, to perform DNS lookups (resolve network names on the 
internal network). 

The DHCP server provides host, IP gateway, DNS server, and NTP server addresses to endpoints 
located on the internal network. 

The router device acts as the gateway for all internal network devices to route towards the DMZ (to the 
NAT device internal address). 

A logging server for Syslog messages (see Step 14: Logging server configuration (Optional)). 

A management and scheduling server (see Step 13: Cisco TMS configuration (Optional)). 

The Cisco VCS Expressway is a SIP Registrar & Proxy and H.323 Gatekeeper for devices which are 
located outside the internal network (for example, home users and road warriors registering across the 
internet and 3

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 party businesses making calls to, or receiving calls from this network). 

The Cisco VCS Expressway is configured with a traversal server zone to receive communications 
from the Cisco VCS Control in order to allow inbound and outbound calls to traverse the NAT device. 

Note: The Cisco VCS Expressway has a public network domain name. 

For example, the Cisco VCS Expressway is configured with an externally resolvable name of 
vcse.example.com (which resolves to an IP address of 192.0.2.2 by the external / public DNS 
servers). 

Cisco VCS Deployment Guide: Basic Cisco VCS configuration – Cisco VCS Control with 
Cisco VCS Expressway 

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