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 incoming calls

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.

An unregistered endpoint (one that is not registered to any system) 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 (for example,

[email protected]

). The VCS will then 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 Expressway is neighbored with an VCS Control for firewall traversal, you should typically set

Calls to

unknown IP addresses

Indirect

on the VCS Control and

Direct

on the VCS Expressway. 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 VCS Control 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 Expressway to see if that

system is able to place the call on the VCS Control’s behalf.
The VCS Expressway 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 H.323 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.

To configure how the VCS will behave 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 Service

•