The nature of an analog modem and a phone line limits
it to connecting to one phone number at a time, and
if one application is using the modem to connect to
a certain phone number, it would not be possible for
another application to dial out to another phone number
on that modem at same time.
However, Windows has a feature called "Internet
Connection Sharing" which can allow a PC to share
one internet connection with other PCs on their local
network. It does not matter if the source of the internet
connection is thru a Dial-Up Networking (DUN) modem
connection, or a full time connection such as DSL,
cable, etc. NetModem can be used to make a DUN connection,
and this DUN connection could be shared just as if
it had been done on a local modem.
For dialup applications other then DUN, you would
need either multiple modems or a multi-modem card,
and multiple phone lines. NetModem is designed to
"pool" multiple modems, so each time another
user needs to dial out, the next modem in the pool
is automatically assigned to them.
Windows Server (And Windows RAS) are not required
for NetModem to operate. If RAS is installed
on the NetModem Server PC, NetModem Server will allow
modems to be pooled both by RAS (for Dial-In) and
by NetModem Server (for Dial-Out). Each time a client
requests a modem, NetModem Server will ask RAS if
a modem is currently in use, and if RAS says its available,
NetModem Server will borrow that modem from RAS, returning
it to RAS's use after the client is finished with
it.
Is Active Directory required to support User Authentication?
Active Directory is not required for User Authentication,
and you can locally authenticate on a network without
a domain controller by simply defining users and groups
on the NetModem Server PC. Multiple Active Directory
and NT4 domain controllers are supported.
NetModem Server allows each pool of modems be individually
configured for user authentication. If user authentication
is enabled for a pool, only the users and groups defined
in that pool properties access list will be given
access.
Why am I not finding Active Directory users or
groups in the NetModem Server access list?
NetModem Server version 2.x required that Active
Directory users/groups were defined as global users
or global groups. If the users are defined as a domain
local user or a domain local group they would not
be seen by NetModem Server version 2.x (Unless the
NetModem Server PC is also the Domain Server).
As of version 3.0, all Active Directory users and
groups can be seen by the NetModem Server.
When I install NetModem Server on NT 4.0, it says
activeds.dll not found. How do i fix this?
NetModem Server requires the Active Directory Client
to be installed on the NetModem Server PC.
Active Directory Client is included in all versions
of Windows XP, Vista, and 200x, but for Windows NT
4.0 you will need to download the Active Directory
Extention for NT 4.0 from Microsoft's web site. Additional
information can be found here: http://pcmicro.com/netmodem/support_nt4.html
Does NetModem support multiple modem pools?
Yes, NetModem allows multiple pools to be defined
in the server. Each modem pool can contain one or
multiple modems, and all the modems in the pool share
the same properties and security settings.
Yes, this can be done by selecting "Automatic
Pooling" from the NetModem Client Configuration
Window for the "Remote COM port to connect to".
Yes, as long as the modems on the server support
Class 2 or Class 2.0 fax and the PC faxing software
you are using must also be configured to use Class
2 or Class 2.0. Most third party Faxing programs including
WinFax Pro allow this. Unfortunatly the MS-Fax service
included with Windows is hardcoded to only support
class 1 fax. Class 1 is timing sensitve and therefore
can not be used over a virtual COM port. For more
information please refer to the faxing
issues page.
NetModem allows using a modem for inbound modem data/fax
calls by a client PC, but this would cause the modem
to be constantly in-use by the client
that is holding the Modem port open while listening
for an incoming RING, thereby preventing other clients
from using this modem during that this time.
For receiving inbound fax calls, a better solution
would be to have the MS-Fax service (or another Fax
program such as WinFax Pro) accept inbound calls on
the modem directly from the NetModem Server PC. NetModem
Server is able to tell MS-Fax or WinFax to release
the modem when a NetModem client PC requests to use
a modem for dialout, and after the client releases
the modem it is then returned to the Fax software.
For receiving inbound DUN (Dial Up Networking) calls
on the modems, you can enable Microsoft RAS (Remote
Access Server) on the NetModem Server PC, allowing
NetModem Server to share the modem resources with
RAS. Then when a client requests a modem, NetModem
Server will ask RAS if the modem is currently available,
and if it is, NetModem Server will borrow the modem
and return it to RAS after the client releases it.
If the Network Administrator does not want to allow
the NetModem Client PC's to be able allow applications
such as pcAnywhere to accept incoming modem calls,
a pool of modems can be configured to block Dial-In.
This option is found under Pool Properties in NetModem
Server.
When a client application attempts access a modem,
but all the shared modems on the server are currently
in-use by other clients (or local applications on
the Server PC), the client will receive a pop-up message
on their screen indicating that NetModem Server does
not have any available modems. This pop-up message
can be disabled in a client under the "Advanced"
settings button. The client application will be told
that the Modems COM port could not be opened, due
to being in use by another application.
When attempting to add a modem driver to the client's
virtual COM port, the COM port is not listed. Why?
Some Plug-and-Play modem drivers (Including US Robotics
an Multitech external modems) will fail to see a modem
attached to a virtual COM port by default. This is
also true for most Software based modems (commonly
called WinModems), which look for PCI or USB hardware
to be present before allowing a COM port to be selected.
If you encounter a modem driver which fails to list
the NetModem Client's virtual COM port when attempting
to install it on the NetModem Client PC, it could
be the above reason, or it could also occur if the
virtual COM port has not been configured with an incorrect
IP address, preventing it from reaching the physical
modem on the NetModem Server PC. First verify that
your NetModem Client COM port is configured properly,
by going to the "NetModem Client Configuration",
selecting that COM port, and run the "Test Server
Connection" to verify that the modem on the server
is detected.
If the test is successful, then please contact a
PC Micro support engineer and provide your modem driver
.INF file, and we can modify it to allow installing
it on a virtual COM port.
NetModem Client may need to update the routing table
to ensure that it allows the NetModem Server to remain
reachable. This is nessesary because a Dial-Up Networking
(PPP) connection will change the routing table to
reach the DUN destination. Each time a NetModem Virtual
COM port is opened, the default action is to update
the routing table as needed to allow the NetModem
Server to always remain reachable. If there are multiple
default routes in the table, NetModem Client will
use the first default route to determine a new route
which might need to be added.
Problems can appear if the route table has default
route(s) which are bad, for example, if the IP address
listed as the gateway doesn't exist or is unreachable.
If the only default route is bad, or the first one
of multiple default routes are bad, it is likley you
will experience a problem when creating a Dial-Up
Networking conection. If NetModem Client needs to
create a specific route for a NetModem Server which
is on a different subnet, it will use that unreachable/non-existant
gateway, which then renders the NetModem Server PC
as unreachable.
NetModem Client will implement incorrect specific
routes only if the routing table is misconfigured
and/or reports invalid information..
Depending on its configuration on your network,
the keep-alive feature of the TCP/IP protocol takes
a long time (10 to 15 minutes) to differentiate between
a merely idle connection and a broken one. The TCP
protocol opts to err on the side of keeping a possibly
idle connection open.
To improve on this, NetModem Client and NetModem
Server use a separate mechanism to detect lost connection
in approximately one minute.
A small time delay (known as latency) is added when
communicating over a network, compared to using a
local serial port and modem. There is a small number
of applications that are sensitive to latency, The
most common is Class 1 fax applications. Therefore
we do not reccomend using NetModem with class 1 fax
applications.
Dial-Up Networking will always add a new "default
route" to the TCP/IP routing table once a DUN
session is started. If the local area network contains
multiple subnets, and the PC connects to those subnets
using a default route in the routing table, the new
default route added by Dial-Up Networking will be
used instead of the original one.
This results in the PC now having access only to the
local subnet, because any TCP packets destined for
the other subnets will be routed to the modem rather
than to the network interface card.
This issue is not unique to NetModem Client, as it
will also also occur on a PC using a local modem.
For more information, see the following Microsoft
Knowledge Base articals:
While these KB Articles only refer to Windows NT, they
also apply to all later versions of Windows.
The solution is to modify the routing table by adding
a static route to the other subnets, as described in
KB Article 140859.
NetModem Client has an option to update the routing
table automaticly when the NetModem Server is on another
subnet. This can be found under the Advanced section
of the NetModem Client Configuration, and is enabled
by default.
On Windows NT, 2000, XP, and 2003, Both NetModem
Client and NetModem Server run as a Windows Service.
Either Service can be stopped or even disabled by
going to the Windows Control Panel under Services,
and configuring the "NetModem Client" or
"NetModem Server" service. It is also possible
to run NetModem Server as a non-service executable.
This means that when the client sent an AT
command to the modem on the server, the modem failed
to respond with OK.
This could be caused by a number of reasons, such
as a defective modem, or selecting a COM port in NetModem
Server which does not have a modem attached to it.
If you encounter this issue, verify that your modem
is working by going to the NetModem Server PC and
running Hyperterminal (found under All Programs
>Accessories > Communications), and select
the COM port value which was added to the NetModem
Server "Assigned to Pool" list. If there
are multiple COM ports assigned, review the Status
tab of NetModem Server to see which COM port the client
was given when the test failed. Once you select this
COM port in Hyperterminal, click OK, and from the
"Port Settings" dialog click OK again to
use the default settings. Then from the white terminal
window type the letters AT and press enter,
to see if your modem is responding with OK
as it should. If the modem responds with OK in Hyperterminal
then contact a PC Micro support engineer for further
assistance.
The 2 most common reasons are a bad phone number
or a modem driver issue.
Phone Number issues:
Verify that the telephone number is entered correctly
(1+area code for long distance, any access codes you
may need for an outside line such as 9 before the
number.) You may also try plugging in a standard analog
phone and try to dial the number to verify that the
phone line supports outbound or long distance calls.
Modem driver Issues:
On the server side check that there is not more then
one modem driver assigned to the COM port, byt going
to Control Panel > Phone and Modem Options >
Modems. If more then one modem driver is assigned
to the same COM port, NetModem Server will not be
able to open the port correctly.
On the client side check the installed modem drivers
to make sure they match the modem drivers installed
on the server side. if these drivers are not an exact
match it can cause connections to fail due to mismatched
"AT" commands. Therefore it is always best
to use the same version of the manufactures modem
drivers on both the server and clients.
Some modem drivers (most commonly PCI and USB) will
not install on a Client's virtual com port, because
they expect to see the PCI or USB hardware present.
Our support department can modify these modem drivers
for you to allow you to install them.
There are known issues with older versions of the
Digi Acceleport Xp firmware, which can cause advanced
modem applications to fail, hang, or crash. This has
been solved in the current Digi firmware, which is
a free downloadable update available from Digi's web
site here: http://www.digi.com/support/productdetl.jsp?pid=1374&osvid=0&tp=2
No. They are independent from each other.
Assuming NetModem Server is installed
on the ISA Server PC, and the NetModem clients are
on the internal network, You will need to define the
following two rules in ISA Server, one for inbound
traffic and one for outbound traffic:
Rule 1
NetModem Server version 3.33 or 3.34 uses a new version
of InstallShield 2008 which under some conditions
could result in this installer error when trying to
uninstall or upgrade to a newer version. This can
be resolved by performing a manual uninstall as shown
on the
Solving Error 1721 page.
How can I remotly deploy NetModem Client with pre-configured
COM ports?
This can be done by passing the installer a registry
configuration file for the Virtual COM port settings
on the command line. Please review the
NetModem
Unattended Installation tips for details.
NetModem uses the latest version of OpenSSL, currently
version 0.9.8h. OpenSSL is an Encryption Library that
allows a secure connection between the server and
the client connections.. Over the years, security
exploits and vulnerabilities have been discovered
in OpenSSL from time to time, and when this happens
the OpenSSL team releases an updated version to fix
such issues. Due to the importance of such issues,
we will release a new version of NetModem within a
few days of a new version of OpenSSL being released.
In order to use the encryption feature you will need
a license key that enables encryption. Because encryption
is not avalible in all countries the evaluation version
has the encryption feature disabled by default. Contact
your account manager if you require encryption.
The sample SSL certificate included with NetModem
server is not signed by a Certificate Authority, so
when testing with this certificate the client should
be configured to *not* require a signed certificate
(found under advanced options in the client configuration).
The sample certificate should only be used for testing
purposes, as it uses a known password and is therefore
not truly secure.
If you need assistance with encryption please go
to the support section of our web site and a fill
out a support
request.
