using an H.323 URI (if the DNS system
has been appropriately configured). If URI
dialing is used, DNS is queried for a call
signaling address and, if found, the call is
placed to that address. (See

URI Dialing

for details of how to configure the Call
Signaling SRV Record.)
dialing its IP address

However, it is sometimes undesirable for a
system to be allowed to place a call to an
IP address directly. Instead, you may want
a neighbor to place the call on behalf of the
VCS, or not allow such calls at all. The VCS
allows you to configure this behavior.

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An unregistered endpoint can call an endpoint registered with the local VCS.
If there are no firewalls between the unregistered endpoint and the locally registered endpoint, it is possible for the caller to place the call by dialing
the locally registered endpoint’s IP address. However, we do not recommend that callers are given IP addresses to use as the call may not always be
successful (for example if the IP address is private).
Instead, we recommend that callers from unregistered endpoints dial the IP address or the domain name (if configured) of the local VCS, prefixed by
the alias they wish to call. The VCS will then resolve the alias and place the call as normal.

An unregistered endpoint is any device that
is not registered with an H.323 gatekeeper
or SIP Registrar (e.g. VCS, gatekeeper or
Border Controller). Although most calls are
made between endpoints each registered with
such a system, it is sometimes necessary
to place a call to, or receive a call from, an
unregistered endpoint.

Calls to an Unregistered Endpoint

Recommended Configuration for

Firewall Traversal

When the VCS Border Controller is neighbored
with an internal VCS for firewall traversal,
you should typically set

Calls to unknown IP

addresses

Indirect

on the internal VCS and

Direct

on the VCS Border Controller. When a

caller inside the firewall attempts to place a
call to an IP address outside the firewall, it
will be routed as follows:

The call will go from the endpoint to the
internal VCS with which it is registered.
Since the IP address being called is not
registered to that VCS, and its

Calls to

unknown IP addresses

setting is

Indirect

the VCS will not place the call directly.
Instead, it will query its neighbor VCS
Border Controller to see if that system is
able to place the call on the internal VCS’s
behalf.
The VCS Border Controller receives the
call and since its

Calls to unknown IP

addresses

setting is

Direct

, it will make

the call directly to the called IP address.

About Unregistered Endpoints

Calls from an Unregistered Endpoint

Calls to Unknown IP Addresses

Determines the way in which the VCS will manage calls to IP addresses which are not registered
with it or one of its neighbors.

Direct:

A locally registered endpoint will be allowed to make the call to the unknown IP address

without the VCS querying any neighbors. The call setup would occur just as it would if the far end
were registered directly to the local system.

Indirect:

Upon receiving the call the VCS will check to see if the IP address belongs to one of its

locally registered endpoints. If so, it will allow the call. If not, it will query its neighbors for the
remote address. If the neighbor’s configuration allows it to connect a call to that alias, the VCS
will pass the call to that neighbor for completion.

Off:

This will not allow any endpoint registered locally to the VCS to call an IP address of any

system not also registered locally to that VCS.

Calls to and from Unregistered Endpoints

Configuration

To configure the VCS’s behavior when
receiving a call for an IP address that is not
registered locally:

VCS Configuration > Calls

You will be taken to the

Calls

page.

xConfiguration Call Services

CallsToUnknownIPAddresses

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