OfficeConnect ISDN LAN Modem Frequently Asked Questions
Firmware Version 5.3.1 (released 9 November '99)Are you
using the latest firmware? Click here
to find out.
Last Update: 15 November '99
Product Features and
Capabilities
The LAN (Local Area Network)
Data
Calls
Voice
Calls
Management and Security
Applications
Information for the technically minded
Product Features and Capabilities
Q. What is a LAN Modem?
A. Typically, most people start out with just one workstation
with a modem attached. As their needs grow, and they require more
workstations, it becomes necessary to network your workstations
together, and to share modems and phone lines. This is where the LAN
Modem comes in. It allows you to network your workstations together,
and share the modem between them.
The LAN modem is essentially an ISDN router with a built-in
Ethernet hub. It eliminates the COM port speed bottleneck (because
the LAN is running at 10 Mbps in comparison to a 115 Kbps or 230
Kbps serial port rate), and at the same time provides local
networking (for file and printer sharing) between the attached
workstations.
With the latest firmware, you can also dial into a LAN Modem.
This allows you to connect 2 LAN's together, or to have user dial
into the LAN to access servers.
Q.
What Operating Systems does the LAN Modem support?
A. The LAN Modem supports all operating systems with a TCP/IP
stack, which includes Windows 95/98 and NT, Apple Macintosh, Unix
and Linux. To configure the LAN Modem, the only software you need on
your PC is a web browser.
Q.
What protocols work with the LAN Modem?
A. The LAN Modem supports all networking protocols (such as IP,
IPX and AppleTalk) on the local LAN. However, only IP traffic is
passed over the ISDN connection.
Q.
How many workstations can I connect to the LAN Modem?
A. The LAN Modem has a built in 4 port hub. However, you can
connect the LAN Modem to a hub. This allows you to connect the LAN
Modem to large networks with many workstations. The limitation is
that only 25 workstations on the LAN can use the LAN Modem for ISDN
access to the Internet or remote network. It makes no difference
whether the workstations are directly connected to the LAN Modem or
connected to a hub that is connected to the LAN Modem. An OfficeConnect
hub is an ideal way to connect 25 workstations to your LAN.
Q. Can I plug the LAN Modem into
my existing IP-based LAN?
A. Yes, however, consider the following. It is best to connect
the LAN Modem to one PC initially, to ensure successful
configuration. The LAN Modem will need a static IP address and
subnet mask that is in the range of the rest of your network. If you
already have DHCP server functionality on your existing IP-based
LAN, or if you are using static IP addressing, then disable the DHCP
server on the LAN Modem. Please refer to the User Guide for
more information.
Q. Can I plug
the LAN Modem into my existing non IP-based LAN?
A. Yes. However, you will have to install a TCP/IP stack and a
Web browser on each of the workstations. After you have installed
TCP/IP and a Web browser, refer to the Getting
Started Guide for the instructions on setting up
TCP/IP and configuring the LAN Modem.
Q.
How do I connect my LAN Modem to a hub?
A. The Ethernet cable supplied with the LAN Modem is a
straight-through cable. This is the correct cable to connect a PC to
the LAN Modem. However, if your connect your LAN Modem to a hub, you
need a cross-over cable. A cross-over cable has the receive and
transmit pairs of wires "crossed". Some hubs have a switch next to
one of the ports that can change a straight-though cable to a
cross-over cable. This switch is usually labeled "MDI/X" or "hub".
Connect one end of the Ethernet cable to this port, and the other
end in any of the LAN Modem's ports. Press this switch until the
LED's on both the LAN Modem and the hub are lit - showing that they
are connected to each other.
Q. Can I
plug the LAN Modem into my LAN with 40 workstations? Only 25 of them
need Internet access.
A. Yes. All 40 workstations can participate in local networking
on the LAN, but only 25 can access the Internet. To successfully
configure your LAN, you need to follow the following steps:
- You need to select a suitable subnet mask for your LAN. A
subnet mask of 255.255.255.0 will give you 254 addresses (0 and
255 are broadcast addresses). Please refer to other sources for
information on TCP/IP and subnet masks.
- You must select up to 25 workstations to have access through
the LAN Modem.
- If you currently have a DHCP server on the LAN you should
disable it. The LAN Modem gives access to workstations based on IP
address; if the IP address of the workstation changes (and it can
if you use DHCP) it will no longer have Internet access.
- The LAN Modem must be given a static IP address. The default
IP address of the LAN Modem is 192.168.1.1. You could allocate
addresses in the range 192.168.1.2 to 192.168.1.254 to your
workstations.
- On each of the selected 25 workstations, enter the
workstation's unique IP address (selected from the above range),
the gateway address (192.168.1.1), the DNS address (192.168.1.1)
and the subnet mask (255.255.255.0).
- On each of the other 15 workstations, enter the workstation's
unique IP address (selected from the above range), DNS server
(192.168.1.1) and subnet mask (255.255.255.0). There is no need to
enter a gateway address, since these workstations do not have
access to the Internet or Private Network.
- Go to the LAN Modem's main configuration screen.
Click on LAN Parameters. Enter the unique IP address
assigned to the LAN Modem (if different from its default address
of 192.168.1.1), the subnet mask (255.255.255.0) and disable the
DHCP server. Click the Submit button.
- The IP addresses of the 25 selected workstations must now be
configured on the LAN Modem. To do this, go to the LAN Modem's
main configuration screen, and click on Workstations. Go to
each workstation entry in turn, and enter the IP address of each
of the 25 workstations. Remember to check the box labeled IP
Address Statically Configured on Workstation.
Q. My LAN needs more bandwidth. Can I have
2 LAN Modems on the same LAN?
A. Yes. Essentially you'll be dividing your LAN into two logical
halves, with some workstations using one LAN Modem, and the rest
using the other. It is not possible to combine the bandwidth of the
two LAN Modems. Here's how to go about configuring this:
- The LAN Modems have the same default IP address. You will need
to change one of them to a different value. Using the above
example, you can change the IP address of one of the LAN Modems to
192.168.1.2.
- You might need to select a different subnet mask for your
network. In the above example, a value of 255.255.255.0 was
chosen. This gives 252 IP addresses that can be allocated to
workstations on the LAN.
- A DHCP server issues IP addresses to workstations on the LAN.
The LAN Modem has a built-in DHCP server, but you cannot have 2
DHCP servers on the same LAN. To simplify this example, the DHCP
servers in both LAN Modems have been disabled. It is possible to
leave one of the DHCP servers enabled though.
- You now need to configure the network information on each of
your workstations:
- IP Address (in this example, the IP address range
192.168.1.3 to 192.168.1.6 was used)
- Subnet Mask (in this example, a subnet mask of 255.255.255.0
was chosen)
- Gateway - the IP address of the LAN Modem to use for
Internet access
- DNS Server - the IP address of the LAN Modem to use for
Internet access
- You'll need a separate ISP account for each LAN Modem. Most
Service Providers don't allow two simultaneous connections using
the same account.
For more information on configuring a
network like this, please consult a good reference book on IP
networking.
Q. Can I plug the LAN
Modem into my 100BaseT (Fast Ethernet) LAN?
A. Not directly. The LAN Modem only supports 10BaseT (10 Mbps).
If you want to connect the LAN Modem to your LAN you'll need a
either a dual-speed (like the OfficeConnect Dual Speed Hub 8 - 3C16750A)
or a switch (like the OfficeConnect Dual Speed Switch 4 - 3C16733A).
Q. Can my LAN Modem connect to 2
different destinations simultaneously?
A. Yes. You can configure the LAN Modem so one B channel goes to
your Internet Service Provider, and the second channel goes to your
office. The LAN Modem will intelligently route information to the
correct destination.
Also, if you configure both connections to use Add Second
B-Channel As Required, the LAN Modem has a unique feature -
Dynamic Bandwidth Allocation! For example, if you have both B
channels connected to your Internet Service Provider, and you launch
an application that requires a connection to your office, the LAN
Modem will automatically drop one of the B channels to your Internet
Service Provider and establish a connection with your office.
Q. Can I setup the LAN Modem for remote
dial-in?
A. Yes, using the latest
firmware. The latest firmware allows you to connect 2 LAN's
together, or to dial into your LAN Modem to access servers.
Remember, only an ISDN modem (or another ISDN LAN Modem) can dial
into an ISDN LAN Modem. If you want to dial into a LAN Modem using
an analog modem, then you need the 56K LAN Modem (3C886).
Q. Can I send and receive faxes with my
LAN Modem?
A. No. However, you can connect a fax machine to one of the phone
ports of the LAN Modem, and send and receive faxes that way.
Q. Can my LAN Modem dial into an analog
modem?
A. No. Your LAN Modem uses ISDN, which is digital. It cannot
connect to an analog modem.
Q. Does the
LAN Modem support CAPI?
A. No. CAPI is the Common ISDN Application
Programming Interface. It is used where the workstation has sole
control of the ISDN device. The LAN Modem is shared amongst many
workstations, so CAPI support is not possible.
Q. How can I check to see if my LAN
Modem is using the latest firmware?
A. From your LAN Modem's main configuration screen, go
to Statistics, then System. Look for the System
software version number. The latest firmware is 5.3.1. If you
are not using the latest firmware you should upgrade your LAN Modem
to obtain all the latest features.
Q. Is the LAN
Modem Year 2000 compliant?
A. Yes.
The LAN (Local Area
Network)
Q. What is the
difference between Static Assigned IP addressing and Dynamic?
A. IP addresses for public networks must be unique and provided
by the Network Information Center (NIC). Because of the increasing
popularity of the Internet, the NIC is running out of permanent IP
addresses. It is therefore becoming more common to use dynamic IP
addresses which are assigned temporarily and then reused, rather
than static IP addresses which are permanent.
For example, when accessing the Internet, your Internet Service
Provider has a pool of IP addresses it uses to provide temporary
connections to multiple users. Once you disconnect from the
Internet, the IP address you were using is placed back in the pool
for use by another user.
If your LAN will not connect to the public Internet, you can set
up your own unique (that is, private) IP address numbering. IP
addresses for private networks such as an office LAN must also be
unique but only within that LAN.
Q. Do my workstations need to be
configured to get an IP address dynamically from a DHCP server?
A. No. If your network is already using static IP addressing
there is no need to change your addressing scheme. However, on
each workstation, you should ensure that the first DNS server
entry exactly matches the IP address specified as the workstation's
gateway address. When the LAN Modem is attached to the computer, the
LAN Modem will automatically change its IP address to match what you
specify in the Gateway IP address on your computer's TCP/IP setting.
Since the LAN Modem will learn and use the Gateway IP address
specified on your computer, make sure that IP address is not being
use by any other workstation on the LAN. For more information, refer
to the LAN Modem User Guide or the web support tip Configuration
for Static IP Addressing (pdf file).
Q. Can I run PC Anywhere on a workstation
on the LAN, and connect to it from the Internet?
A. Yes. Go to the LAN Modem's main configuration screen.
Click on Service Providers and select the entry for your
Internet Service Provider. Click on Select. Scroll down the
page until you get to Default Workstation. Make sure this is
the PC running PC Anywhere.
When the LAN Modem is connected to the Internet, go to the LAN
Modem's main configuration screen.
Click on Statistics, then Current Call. The field
IP address in use gives the IP address assigned to the LAN
Modem by the Internet Service Provider. When you use PC Anywhere to
connect to this IP address, the LAN Modem will forward the packets
to the default workstation.
Your Internet Service Provider might be able to assign your LAN
Modem the same IP address every time it connects. This will
eliminate the need to look up the address assigned to LAN Modem
every time you wish to run PC Anywhere. Speak to your Internet
Service Provider for more information on this.
Q. Upon initial set-up, communication
between the LAN Modem and my computer cannot be established.
A. The LAN Modem is not like an ordinary modem; it does not have
a driver or installation software for your PC. It connects to your
workstation's network interface card (NIC). Read the Getting
Started Guide that came with the LAN Modem for more information
on hardware setup.
Other problems may be caused by one of the following:
- The wrong cable may be connected to the LAN port on the LAN
Modem and your computer. Make sure you are using the 8-pin to
8-pin cable labeled Ethernet that was provided with your
LAN Modem. If you are using another 10BaseT Ethernet cable, it
must be a straight-through cable. Make sure that the LAN status
LED corresponding to the port to which your computer is connected
is lit, indicating that the LAN Modem detects the Ethernet signal
and operation is normal.
- Your Web browser may not be set to a default start page. Enter
a default URL from within your Web browser. If you are using
Internet Explorer, launch your Web browser. From the View menu
select Options. From Page, select Start Page and
then enter an address in the address field such as
http://www.3com.com. If you are using Netscape, launch your Web
browser. From the Options menu, select General Preferences.
From Browser Starts With, select Home Page Location and
then enter a URL such as http://www.3com.com.
- Your Web browser may be configured to use a proxy server,
instead of the LAN Modem. If you are using Internet Explorer,
launch your Web browser. From the View menu, select Internet
Options, then select the Connection tab. Under the
Proxy Server header, uncheck the box labeled Accessing the
Internet using a proxy server. If you are using Netscape,
launch your web browser. From the Edit menu, select
Preferences. Double-click on Advanced, then click on
Proxies. Check the box labeled Direct Connection to the
Internet.
- If your workstations are statically
configured, each with a unique IP address, then the LAN Modem
would have changed its factory default IP address (192.168.1.1) to
match that specified as the Gateway of your workstation. For
Windows '95 and Windows NT, go to Control Panel, then
Network. Select TCP/IP and click on
Properties. Make a note of the IP address of the first
Gateway entry. Make sure that the first DNS (Domain Name Server)
entry matches this IP address. Enter this address as the URL in
your web browser. Make sure that the Gateway and DNS server
configured on all your workstations on the LAN matches this IP
address.
- An incompatible IP address on your computer. Reset the IP
address on your computer. For Windows 95 users, run Winipcfg.exe.
Select the Ethernet adapter connected to the LAN Modem. Click
Release All and then click Renew All. For Windows NT 4.0 users,
run ipconfig and /release and then /renew. For Mac users, from the
Apple menu, select Control Panels and then select TCP/IP. Make
sure Ethernet is selected in the Connect via field. From the
Configure field, select Manually to clear the fields and
then select DHCP. The fields should now read <will be
supplied by server>. Select File and then Close and save
changes when prompted.
- There may be a configuration problem. Reset the LAN Modem to
the factory default setting. Disconnect the ISDN cable from the
LAN Modem and then connect an analog telephone to one of the phone
ports. Lift the handset and press **3266# and then replace the
handset. Reconnect the ISDN cable, restart your computer, and then
launch your Web browser.
Q. A workstation was replaced,
but the new one cannot communicate with the LAN Modem.
A. The LAN Modem can dynamically assign IP addresses to 25
computers. If you have replaced one of these 25 computers since the
IP addresses were assigned, you must release the IP address assigned
to the computer you removed before the LAN Modem can assign an IP
address to the newly attached computer.
To do so, from another computer attached to the LAN Modem, go to
the LAN Modem's main configuration screen.
Click on the PC icon in the illustration. From the PC Parameters
window, select the name of computer you removed and then click
Select. From the PC Parameters window for that workstation, click
Release PC Entry. The newly added PC can now be assigned an IP
address.
Also note that if all 25 computers using dynamic IP addressing
are replaced (because the LAN Modem was relocated, for example) you
have to do one of the following in order to allow the LAN Modem to
assign dynamic IP addresses to these computers.
- Restore the LAN Modem to its factory default setting by
connecting a telephone to one of the Phone ports (disconnect the
ISDN line) and then press **3266# from the handset. The LAN Modem
will then need to be reconfigured. Refer to the Getting
Started Guide for instructions on how to do this.
- Configure your computer with a static IP address on the same
LAN as the LAN Modem, release the PC entries, and then reconfigure
your computer to use dynamic IP addressing.
Data Calls
Q. Calls continue to reconnect or calls
do not time-out and disconnect.
A. This may occur because an application or LAN device is sending
IP packets. If you are running Windows '95 / '98 or Windows NT, take
a look at the following technical articles on Microsoft's web site
(www.microsoft.com):
- Article Q134985: Browsing & Other Traffic Incur High Costs
over ISDN Routers
- Article Q119493: NetBIOS over TCP/IP Name Resolution and WINS
- Article Q137368: How to Disable NetBIOS Name Resolution on DNS
One solution to the above NetBIOS DNS request problem is
to call your domain (Windows NT terminology) or workgroup (Windows
'95 / '98 terminology) "lanmodem". The LAN Modem will then return
it's own IP address, instead of making a call to resolve the NetBIOS
DNS request.
Other Windows '95 / '98 / NT solutions to NetBIOS or WINS
requests bringing up the ISDN line:
- You can prevent NetBIOS packets from bringing up a call by
enabling NetBIOS filtering. To do this you must be using the
latest firmware.
Go to the LAN Modem's main configuration screen.
Click on LAN Parameters and make sure the box labeled
Enable NetBIOS filtering is checked. Click on
Submit. This will prevent packets to ports 135, 137, 138
and 139 from initiating a call, but traffic to these ports will be
passed once the call is up. This might have the undesired effect
of resetting the idle timer and thus prevent the call from being
dropped. To work around this problem you can do one of two things.
Firstly, you can set your idle timeout lower than the frequency at
which NetBIOS automatically generates packets. A setting of 89
seconds or less (the default is 30 seconds) will accomplish this.
The second option is to manually disconnect the call each time a
call is made.
To set the idle timeout to a lower value, go to the LAN Modem's
main configuration screen. Click on Data Call Parameters.
Set Disconnect an automatic data call after how long of an
inactivity period? to 89 seconds or less. Click on the
Submit button. To manually disconnect a call, go to the LAN
Modem's main configuration screen.
Click on Manual Calling. Click on Hang Up.
- If you are not using local file and print sharing on
the local LAN, you can disable it. You can do this by selecting
Control Panel -> Network ->
Configuration tab. Click on File and Print Sharing.
Uncheck both boxes and click on OK.
- NetBIOS can use either TCP/IP or NetBEUI as the transport
layer. The LAN Modem will ignore NetBEUI traffic, so you can elect
to use NetBEUI instead of TCP/IP:
- Select Control Panel -> Network ->
TCP/IP -> Bindings. Make sure that Client
for Microsoft Networks is unchecked.
- Select Control Panel -> Network ->
NetBEUI -> Bindings. Make sure that Client for
Microsoft Networks is checked.
- If you are not using a Windows Internet Name Service (WINS)
server, you should disable it. You can do this by selecting
Control Panel -> Network ->
Configuration tab. Click on TCP/IP then click on
Properties. On the WINS Configuration tab, click
Disable WINS Resolution. Click on OK, then
OK.
Other applications running in background may be
bringing up the call. If you are running Windows '95 or Windows 'NT
press Ctrl-Alt-Del to see all the applications running on your
workstation. For example, Semantec's Norton Utilities keeps the line
up with a ping to "ping.semantec.com" every 2 seconds.
The LAN Modem can give you information on the packet that caused
the call to be made. Go to the LAN Modem's main configuration screen,
and click on Statistics. Click on either Current Call
or Last Call to see why the call was made.
Q. A Multilink PPP call cannot be placed.
Only one B channel connects.
A. There a number of possible reasons for this:
- Your LAN Modem may not be configured to use Multilink PPP.
From the LAN Modem's main configuration screen,
click on Service Providers. Select the service provider
from the pull-down list, and click Select. Under
Bandwidth Allocation make sure that either one of the
following options are checked: Use Two B Channels, or
Add Second B Channel As Required.
- There may not be enough traffic to reach the threshold for
adding the second B channel. To verify the threshold settings, go
to the LAN Modem's main configuration screen.
Click on Data Call Parameters and verify your settings.
- An inability to connect both channels of a Multilink PPP call
may be due to an incompatibility with the router into which you
are dialing. Some service providers may split the two B channels
of a Multilink PPP call between different routing devices,
preventing the channels from being linked together. This is
usually most prevalent during high peak hours. If you are unable
to establish a Multilink PPP call, try reconnecting your call
during off-peak hours. If you are still unable to establish a
Multilink PPP call, contact your Internet Service Provider to
confirm that they support this feature.
- You can also confirm whether the LAN Modem was able to
negotiate Multilink PPP with your service provider's router. When
one channel is connected, go to Statistics then Current
Call. If the Data Call options states PPP (and not
Multilink) then your service provider's router does not
support Multilink.
- Your service provider might have configured your user account
to only use one B channel. Check with them to confirm that your
account allows a 2 channel connection.
Q. Although only one data call is
connected, another data call cannot be placed.
A. The call that is already connected may be configured to always
use two B channels, thereby leaving no bandwidth available for
another call. Check the bandwidth allocation setting for that
service provider.
Q. I can't
get Tollmizer to work. Why not?
A. Tollmizer is a great feature of the LAN Modem, allowing it to
place a voice call, but pass data instead. This is useful where the
phone company charges voice and data at different rates; Tollmizer
allows you to save money. This feature is sometimes called
Data-over-Voice.
There are a number of things to check if Tollmizer doesn't work:
- Line provisioning
You ISDN line must be provisioned
to allow voice
calls. Check with you phone company to ensure this is the case.
- The path your call takes through the telephone network
Sometimes the phone company routes voice calls through an
older, non-digital section of its network, preventing you from
passing data over the line.
- The remote router
The router you are connecting to
must be configured to treat voice (analog) calls as digital calls.
Sometimes your Service Provider might give you the same phone
number for both 56K modem and ISDN calls - in this case, incoming
voice calls are treated as analog calls, and will be routed to a
modem bank. If this happens, Tollmizer won't work. Check with your
Service Provider to ensure voice calls are treated as digital
calls.
Q. My default
home page brings up the LAN Modem's configuration screen. Why?
A. Your home page URL is actually cached to the browser memory
with the IP address of the LAN Modem. To clear this, simply go to
your Web browser and clear the cache. If you are using Netscape,
under the Options menu, select Preferences and then click Clear
Memory Cache Now. If you are using Internet Explorer, from the View
menu, select Options and then click the Navigation tab. In the
History section, click Clear History.
Q. How do I configure the LAN Modem to use
PAP instead of CHAP?
A. Password Authentication Protocol (PAP) and Challenge Handshake
Authentication Protocol (CHAP) are used to pass your username and
password to the remote router. When the LAN Modem dials the remote
router it will automatically negotiate the authentication protocol,
and will use which ever authentication protocol the remote router
requests. The LAN Modem will prefer to do CHAP (which encrypts your
password), so if the remote router supports CHAP then this is what
will be used.
Q. Why doesn't CHAP
(encrypted authentication) work when using Windows NT 4.0?
A. Earlier versions of LAN Modem firmware only supported
CHAP-MD5. This is the industry standard. In the latest firmware
release we've added support for MS-CHAP, the proprietary
authentication protocol used by Microsoft.
Q. When downloading from the
Internet for a while, why does my connection hang?
A. Although the LAN Modem uses a standard type of compression,
Hi/fn™ (formerly STAC) compression, and other vendors' equipment
also supports Hi/fn, sometimes the implementations do not fully
adhere to the specification. Therefore, you may experience problems
with compression when dialing into some routers. If you experience
problems with compression, change the value of the Data
Compression field to No in your service provider profile.
If your ISP is using 3Com's Total Control Hub with HiPer ARC,
there is a patch for a compression bug. Ask your ISP to download
Service Release 4.1.59-6 (or later) for HiPer ARC from 3Com's web
site. Please note, version numbers for HiPer ARC count
downwards, so 4.1.65-9 was released before 4.1.59-6 and therefore
does not contain the compression patch.
Q. When dialing into an Ascend
router, what PPP data compression works?
A. Ascend changed their compression algorithm between version 5
and 6 of their firmware. If the Ascend you are dialing into has
version 5.00A or earlier, set the compression on the Ascend to
MS-STAC. If the firmware is 5.00P12 or later, set the compression to
STAC-9. The STAC setting on Max and TNT routers is proprietary, and
will only work between Ascend routers.
Q. What is TempSvcProvider used
for?
A. In the Manual Calling screen, there is an entry called
TempSvcProvider. This entry is used to make a test call to a
Service Provider to verify that a connection can be made to
it. Only the workstation making the test call can pass data to the
remote location. Should other workstations on the LAN wish to pass
data to the remote location, they need to bring up a browser window,
and go to the Manual Calling screen. They should then click
on Join Call.
Q. Can I
have multiple email accounts with my single Internet Service
Provider account?
A. Yes. Email accounts are very different to the account you use
to connect to your Internet Service Provider. Typically, the
Internet Service Provider will give you one email account free of
charge; if you want more your Internet Service Provider will
normally charge a nominal fee for them. Contact your Internet
Service Provider for more information.
Voice Calls
Q. Does the LAN Modem support
supplementary voice features?
A. Yes, with the latest firmware the LAN Modem does support Call
Waiting, Call Conferencing, Call Transfer, etc. Check with your
phone company to ensure that your ISDN line has been provisioned to
use these features. The phone company may charge you to use these
features. Click here
to check if your LAN Modem is using the latest firmware.
Q. How does Caller ID work?
A. In contrast to how Caller ID works over a plain ordinary
telephone service (POTS) line, where it is delivered as a V.23 modem
signal between the 1st and 2nd ring cycles, Caller ID over an ISDN
line is delivered over the D (signaling) channel at the initial
onset of call setup in compliance with ITU-T specification Q.81.3.
However, ISDN Caller ID will not contain any time stamp information.
The LAN Modem, in processing the Caller ID signal, superimposes its
own internal clock (date and time) signal and outputs the combined
information to the POTS port(s) as a V.23 signal, allowing
conventional Caller ID display units to function. This information,
like an ordinary POTS line, is generated between the 1st and 2nd
rings. If the time displayed with the call is incorrect it is
because the LAN Modem's internal clock is incorrect and since the
LAN Modem gets its date and time info from the workstation, it is
likely that the workstation's date and time is incorrect.
In most cases, you need to subscribe to the Caller ID service
from your phone company. They may charge a fee for this service. If
you have subscribed to the Caller ID service, but the Caller ID box
attached to the LAN Modem is not displaying the Calling Party's
number, take a look at Statistics, Last/Current Call.
If the Calling Telephone Number is not present, then check
with your phone company to see if you have Caller ID on your line.
If the Calling Telephone Number is displayed, check that your
Caller ID box is attached to the correct analog port of the LAN
Modem, and is functioning correctly.
For more information on Caller ID, take a look at Testmark's white paper.
When both B channels are in use, Caller ID will not be presented
to the Caller ID box. This is a limitation of the hardware. The LAN
Modem has two Serial Communication Controllers (SCC's). A single SCC
is needed to generate the Caller ID information, but both are needed
to pass data to the B channels.
Q. Can I use a 2-line phone with my LAN
Modem?
A. Yes. However, make sure both lines of the phone are connected
to the LAN Modem. If you connect one line to the LAN Modem, and the
other to an ordinary phone line, a voltage differential can occur
between the 2 lines, potentially causing damage to either your LAN
Modem or the phone - or both! This is especially true during an
electrical storm; having one line attached to your LAN Modem and the
other to an ordinary phone line actually attracts lightning to your
phone line!
Q. Does the LAN
Modem support Caller ID names?
A. Yes. If the phone company sends the LAN Modem the name of the
person calling, the LAN Modem will present that information to the
Caller ID box. Both your Caller ID box attached to the phone port of
your LAN Modem and your phone company have to support Caller ID
names for this to work. Make
sure you are using the latest firmware.
Q. When I check Outgoing Caller
ID Block, Caller ID is still sent. Why?
A. The LAN Modem sets a bit in the outgoing call setup message to
suppress Caller ID. If the telephone switch the LAN Modem is
connected to is configured to respond to this bit setting, then
outgoing Caller ID will be blocked. If you have checked Outgoing
Caller ID Block and Caller ID is still being sent then your
telephone switch is either running older software, or is not
configured to recognize this bit. In this case, you can still block
Caller ID by dialing the usual Caller ID blocking prefix (usually
*67).
Q. Does the LAN
Modem support distinctive ringing?
A. Yes. The phones attached to the phone ports of the LAN Modem
can be made to give a distinctive ring; when a voice call is routed
to one of the LAN Modem's phone numbers, it can be made to ring
differently to a call to the other phone number. To enable
distinctive ringing, go the the LAN Modem's main configuration screen.
Click on ISDN Parameters and enable Distinctive
Ringing.
This is similar to distinctive ringing on an ordinary analog
phone line; in this case you would have one line with up to 3 phone
numbers assigned to that one line. Depending on the number dialed, a
ring distinguishing one number from the others is generated by the
phone company.
Q. Why
can't I get a dial tone from the telephone while I am connected to
the Internet?
A. When setting up your Internet Service Provider connection, if
you set Bandwidth Allocation to Use two B channels, your ISDN
connection will be nailed up for a two data channel connection.
Because both B channels are in use, there is no bandwidth available
for the voice call. To be able to place a voice call while connected
to the Internet, under Bandwidth Allocation for this service
provider profile, select Use one B channel or Add second B
channel as required.
Q. Why
can't I get dial tone from the telephone when I know that one B
channel is available?
A. If your line is provisioned on a Nortel DMS-100® switch, then
regardless of the ISDN Ordering Code you choose, you cannot have
simultaneous voice and data on the same phone number because of a
limitation with the central office switches.
When you make a Multilink call (using the Add second B channel
as required setting), and pick up the phone, the first B channel
(corresponding to your first phone number) is dropped. If you picked
up the phone connected to port 1, you would get dial tone. However,
if you picked up the phone connected to port 2 you would not get
dial tone because that phone number would be used by the data call.
For more information on this topic, please take a look at the document
on ordering ISDN for your LAN Modem.
Q. Why can't my PC Card (or PCMCIA) modem
detect dial tone?
A. Some modems, when sampling the voltage on the LAN Modem's
phone port, interpret the voltage to be that of a digital line and
thus don't give dial tone. For USR / Megahertz modems, add the
following command to the init string: AT~~L0.
Q. How do Supplementary Voice Services
like Call Waiting and Call Conferencing work?
A. Supplementary Voice Services are well documented in the User
Guide.
Q. What should I do
if Voice Services don't work?
A. Read the document
on Ordering ISDN, and contact your phone company to ensure your ISDN
line has been provisioned correctly.
Q. How does Voice Messaging work?
A. Voice Messaging is well documented in the User
Guide.
Management and Security
Q. I've forgotten the LAN
Modem's password
A. The only thing you can do is reset the LAN Modem back to its
factory setting and reconfigure it. Reset the LAN Modem to its
factory default setting by connecting a telephone to one of the
Phone ports (disconnect the ISDN line) and then press **3266# from
the handset. The LAN Modem will then need to be reconfigured. Refer
to the Getting Started Guide for instructions on how to do this.
Q. How do I reset my LAN Modem
back to its factory settings?
A. To reset the LAN Modem to its factory default setting, connect
a telephone to one of the Phone ports (disconnect the ISDN line) and
then press **3266# from the handset. An alternative method is to go
the the LAN Modem's main configuration screen and
click on Maintenance, then Reset and restore factory
defaults.
Q. How can I save
and restore my LAN Modem's configuration?
A. Go to the LAN Modem's main configuration screen.
Click on Maintenance then Enter Firmware Download
Mode. This starts an FTP server on the LAN Modem that runs for 5
minutes. As soon as the countdown starts, FTP to the lanmodem (no
password is necessary). If you get a directory listing (usually by
typing "ls" - but this depends on which FTP program you choose to
use) you will see a file called prof.bin. This file contains
the entire configuration of the LAN Modem. Using your FTP program,
you can "get" and "put" this profile. Remember that the FTP server
only runs for 5 minutes, and it must be running for you to be able
to FTP to the LAN Modem.
Q.
Can I remotely load new firmware onto a LAN Modem out in the
field?
A. Yes, new firmware is downloaded using FTP. This means that you
can dial into the LAN Modem using any ISDN router (including another
LAN Modem) and download firmware remotely.
Q. How do I configure or manage a LAN
Modem out in the field?
A. Dial into the LAN Modem using another ISDN router such as
another LAN Modem. (You can also use an ISDN modem with Dial Up
Networking, refer to Chapter 5 of the User Guide for details.)
The two ISDN routers must be on different networks. Using another
LAN Modem do the following:
- Ensure that the two LAN Modems are on different networks. For
example, one can be on the 192.168.1.x network, and the other can
be on the 192.168.2.x network.
- Create a Private Network entry for the remote router. No user
name or password is needed. You must use an arbitrary numbered WAN
link that is different from the two networks.
- Run your web browser, and enter the IP address of the remote
LAN Modem as the URL. An ISDN connection will be established. You
can now remotely manage the LAN Modem.
Q. Does the LAN Modem support Security
Dynamic's Secure ID?
A. No, but it can be made to work. Click on Service
Providers and select the service provider you want to connect
to. Set Allow Automatic Call Initiation to No. Click
on Data Call Parameters and set Disconnect a manual data
call after how long of an inactivity period to 0. This
will prevent the call from being dropped due to inactivity.
When you want to make a call, first edit the Service
Provider with the new password. Then click on Manual
Calling and place a call to your service provider. When you want
to hang up the call, click on Manual Calling and hang up the
call.
Q. Does the LAN Modem support PPTP
(Point-to-Point Tunneling Protocol)?
A. Yes. PPTP is used to create "tunnels" between clients and a
tunnel server. The tunnel allows secure multi-protocol connections
to be established to a remote private network via a public network,
like the Internet. There is no configuration required on the LAN
Modem for this to work. The LAN Modem can also support other VPN
protocols, like L2TP. For more information, take a look at the VPN
document.
You must be running the latest firmware for PPTP to work. To
check your firmware version, click here.
Q. How secure is my LAN from hackers
on the Internet?
A. The answer depends on whether or not your connection to the
Internet uses Network Address Translation (NAT). For more
information on NAT, click here.
Most users (around 99%) use NAT when connecting to the Internet.
Here are some indications that your connection uses NAT:
- You have a "single-user" account at your Internet Service
Provider.
- Your Internet Service Provider issues a single dynamic IP
address when you connect.
- You do not have a "domain" account at your Internet Service
Provider.
If you are not sure whether of not you use NAT,
contact your Internet Service Provider and ask them if you have a
"single-user" account. If the answer is "yes" then you are using
NAT.
Security implications if you are using Network Address
Translation (NAT)
This section applies to most LAN Modem
users.
- Your Internet Service Provider's router will issue a single,
dynamic IP address to the LAN Modem each time it connects. This
makes it difficult for hackers to return to your LAN, if they ever
find it.
- The LAN Modem is only issued a single IP address by the
Internet Service Provider's router. If a hacker on the Internet
tries to connect to this address, this attack will be forwarded to
the "default workstation". The other workstations on your network
are safe from attack.
- Even with hackers being able to gain access to one
workstation, that workstation is only vulnerable if there is some
kind of server application running on it. Remote control
applications, like PC Anywhere or LapLink are the highest risk.
FTP and web server software is usually safer. If you have any
doubt as to the security of the applications running on your PC,
contact the software vendor for more information.
- The LAN Modem itself cannot be accessed from the Internet.
This means there is no way a hacker on the Internet can change the
configuration of your LAN Modem, nor can they steal your dial-up
password.
To change the "default workstation" to a different workstation,
or to one that doesn't exist, go to the LAN Modem's main
configuration screen. Click on Service Provider and
select your Internet connection. Scroll down until you see
default workstation.
Security implications if you are not using Network
Address Translation (NAT)
- When you are conected to the Internet, a hacker could have
access to any workstation on your LAN, and the LAN Modem itself.
- Workstations on your LAN are vulnerable if there is some kind
of server application running on them. Remote control
applications, like PC Anywhere or LapLink are the highest risk.
FTP and web server software is usually safer. If you have any
doubt as to the security of the applications running on your PC,
contact the software vendor for more information.
- The LAN Modem's configuration can be accessed from the
Internet. Make sure you password protect the configuration of your
LAN Modem! Even if a hacker gains acess to your LAN Modem's
configuration, your dial-up passwords are secure because they are
always encrypted. The worst that could happen is that a hacker
could change or erase your configuration.
To set a password on your LAN Modem, and lock the configuration,
go to the LAN Modem's main configuration screen.
Click on Password.
Applications
Q. Microsoft's NetMeeting
A. NetMeeting is one of the very few applications that responds
to an initial meeting request by using a different port number. For
a more detailed explanation, please read How
does NAT work? below. NetMeeting should operate normally if only
one workstation on the LAN is using the software. Problems may be
experienced when 2 or more users on the LAN use the software at the
same time. This is due to the limitation of Network Address
Translation (NAT).
The workaround to this problem is for the second workstation to
use a different NetMeeting server than the first. To change the
NetMeeting server do the following:
Click the Tools menu in the NetMeeting window, and then
click Options. On the Calling tab, select a different directory
server from the drop-down menu. You may also experience
problems with NetMeeting related to call timeout. For more
information on a work-around for this, click here.
Q. Internet games
A. Some Internet games use complex IP address and port
translation schemes that prevent the game from operating as though
you are directly connected to the Internet using an ordinary modem.
This is a limitation of NAT.
The LAN Modem uses an intelligent NAT algorithm that allows most
applications to work when using just a single workstation on the
LAN, but the game may not work when 2 or more workstations are
playing the same game. To get the best results, go the the LAN
Modem's main configuration screen.
Click on Service Provider and select your Internet Service
Provider. Make sure that the Default Workstation for Incoming
Packets is your primary game-playing workstation.
Q. Xterm / Xsession
A. Xterm and Xsession both use complex IP address and port
translation schemes that prevent them from operating as though you
are directly connected to the remote LAN using an ordinary modem.
This is a limitation of NAT.
The LAN Modem uses an intelligent NAT algorithm that allows most
applications to work when using just a single workstation on the
LAN, but the application may not work when 2 or more workstations
are trying to connect to the same host. To get the best results, go
the the LAN Modem's main configuration screen.
Click on Service Provider and select the appropriate Service
Provider. Make sure that the Default Workstation for Incoming
Packets is your primary Xterm / Xsession workstation.
Q. ICQ / mIRC / Kali '95 / E-trade /
NetMeeting
A. Some applications register their IP address with the server
they're connecting to. When the connection idles out due to
inactivity, and the connection is re-established when the
application wants to reconnect to the server, the IP address
dynamically assigned to the LAN Modem by the Internet Service
Provider might be different to the one originally issued. The server
will detect this, and may refuse the connection.
To prevent this problem from occurring, you'll need to disable
(or increase) the inactivity timer. To do this, go the the LAN
Modem's main configuration screen.
Click on Data Call Parameters. Set the inactivity period to
0 seconds. Note, this setting will prevent the LAN Modem from
dropping the ISDN call, which could result in a large ISDN bill.
Please remember to disconnect the call after each session. To
disconnect the call, go to the LAN Modem's main configuration screen.
Click on Manual Calling and hang up the call.
Q. Sending email is occasionally slow
A. This is a limitation of NAT.
When mail is sent to a SMTP server, the server often responds using
a different port number to that originally supplied by the
workstation. If there is only one workstation actively sending
email, the LAN Modem is intelligent enough to direct the server's
response to that workstation. However, if a second workstation is
sending email to the same server, then the server's response will be
discarded - because the LAN Modem does not know which of the 2 (or
more) workstations is needs to forward the response to. After 30
seconds, the SMTP server will again respond, this time using the
port number specified by the workstation. When this happens, the
sending of the email will commence. So, occasionally, you might see
a 30-second delay before your email is sent.
The workaround for this problem is to co-ordinate the sending of
your email with the other workstations, or for each workstation to
use a different SMTP mail server.
Information for the technically
minded
Q. What is the
telnet interface used for?
A. The telnet interface is an unsupported, untested and
undocumented interface, for use by engineering and support only.
The most common use of this interface is for support to obtain a
trace of the LAN Modem's operation for debugging purposes. There is
no official documentation nor support available for this
interface.
However, a LAN Modem user has created an unofficial guide to
the LAN Modem's telnet interface.
Q. How does the LAN Modem's DHCP
server work?
A. The factory default is for the LAN Modem to have an IP address
of 192.168.1.1 and a subnet mask of 255.255.255.224. It will issue
IP addresses in the range 192.168.1.2 to 192.168.1.26. When
requested by a workstation, the LAN Modem will issue the workstation
with an IP address, DNS address, gateway address, and IP "lease".
The DNS and gateway addresses will be the IP address of the LAN
Modem. The IP lease will be 24 hours - meaning the workstation will
need to re-request an IP address every 24 hours or less.
The IP lease is not honored by the LAN Modem however. The
IP address is considered permanently assigned to the MAC address of
the workstation's Network Interface Card. This has the following
benefits and drawbacks:
Benefits:
- If the LAN Modem loses and regains power, any workstation
requesting an IP address will not be assigned one already used by
another workstation.
- If one workstation has been assigned an IP address and is
powered down (say, over a weekend) it will continue to work when
it is powered on again; another workstation cannot be assigned its
IP address
- Since every workstation will always be issued with the same IP
address, it is possible to prevent specific workstations from
accessing a specific Service Provider.
Drawback:
- If the LAN Modem is moved from one site to another, or a
workstation on the LAN is replaced, the IP address assigned to the
workstations no longer on the LAN have to be manually released
before they are made available to other workstations.
To
release an IP address, go to Workstations and select the
workstation who's IP address you'd like to release. Click on
Release Workstation Entry. To clear the the last entry in the
DHCP table, and reset the LAN Modem to its default IP address
(192.168.1.1), remove the ISDN cable, and type "**3265#" on a phone
handset. To reset the entire LAN modem back to the factory settings
remove the ISDN cable, and type "**3266#" on a phone handset. The
phone handset can be connected to either one of the phone ports.
Q. How does the LAN Modem's
DNS server work?
A. The LAN Modem has a built-in DNS server. This increases it's
functionality and simplicity when compared to other routers - most
of which don't have a built-in DNS server.
The LAN Modem's DNS server can resolve local names, and
"lanmodem". When a Windows PC makes a DHCP request, it sends its
name to the LAN Modem. The LAN Modem associates this name with the
IP address it issued, and uses it to resolve local machine names.
For example, instead of typing "ping 192.168.1.2", you can just type
"ping Fred'sPC".
The LAN Modem also resolves "lanmodem" (or "3com.oc.lanmodem") to
be its own IP address. This allows you to type "lanmodem" as the URL
in your browser to bring up the LAN Modem's configuration screen.
The LAN Modem will also return its own IP address to any
DNS request if it has not yet been configured. This means that when
you first connect to your unconfigured LAN Modem you will see the
LAN Modem's configuration screen no matter what your browser's start
page is.
Having a built-in DNS server has another advantage. You can
define the domain of your office connection (for example,
"3com.com") in your Service Provider configuration on the LAN
Modem. This way, the LAN Modem can resolve all DNS requests ending
in the defined suffix (for example, "my_private_server.3com.com") by
forwarding the DNS request to your office's DNS server, instead of
to the Internet Service Provider's DNS server.
To take advantage of the LAN Modem's built-in DNS server, make
sure that the DNS server on all your workstations is set to the LAN
Modem's IP address. If your workstations get their IP address via
DHCP this is done automatically.
Q. How does NAT (Network Address
Translation) work?
A. In a typical scenario of the LAN Modem dialing an Internet
Service Provider, the Internet Service Provider will dynamically
assign the LAN Modem an IP address. The LAN modem will translate the
source IP address in Internet-bound IP packets to this valid,
routable Internet IP address. When a packet is received from the
Internet, the reverse process happens; the Internet Service
Provider-assigned IP address is replaced with the IP address of the
workstation to which that packet is directed.
For example, assume the workstation (192.168.1.2) is browsing
(TCP/UDP port 80) the 3Com web site (192.156.136.22), and was
assigned a dynamic IP address of 136.22.36.12 by the Internet
Service Provider. Note the source port number is generated randomly
by the workstation, and is normally above the well known
ports (RFC
1700).
|
Packet before translation |
Packet after translation |
|
Source |
Destination |
Source |
Destination |
|
IP Address |
Port Number |
IP Address |
Port Number |
IP Address |
Port Number |
IP Address |
Port Number |
| To Internet |
192.168.1.2 |
1031 |
192.156.136.22 |
80 |
136.22.36.12 |
1031 |
192.156.136.22 |
80 |
| From Internet |
192.156.136.22 |
80 |
136.22.36.12 |
1031 |
192.156.136.22 |
80 |
192.168.1.2 |
1031 |
If a second workstation on the LAN wants to communicate to the
same server, and happens to use the same source port number, then
the LAN Modem will translate the source port number as well as the
source IP address:
|
Packet before translation |
Packet after translation |
|
Source |
Destination |
Source |
Destination |
|
IP Address |
Port Number |
IP Address |
Port Number |
IP Address |
Port Number |
IP Address |
Port Number |
| To Internet |
192.168.1.3 |
1031 |
192.156.136.22 |
80 |
136.22.36.12 |
1032 |
192.156.136.22 |
80 |
| From Internet |
192.156.136.22 |
80 |
136.22.36.12 |
1032 |
192.156.136.22 |
80 |
192.168.1.3 |
1031 |
Intelligent NAT (under Service Provider
configuration) adds some intelligence to NAT. Some server
applications might choose to reply using a different port number.
With Intelligent NAT enabled the LAN Modem will attempt to
route the packet to the workstation currently communicating with
that server. It searches its NAT table for a match of the server's
IP address, and then routes the packet to the workstation that
previously communicated with that server. Of course, if there is
more than one workstation communicating with that one server, the
LAN Modem will be unable to determine which workstation the packet
should be sent to; in this case it will go to the first workstation
where the match is first made. For this reason, applications (like
Microsoft's NetMeeting)
that respond using a different port numbers will only work on one
workstation on the LAN. To work around this NAT limitation, the
second workstation should connect to a different server, if
possible.
|
Packet before translation |
Packet after translation |
|
Source |
Destination |
Source |
Destination |
|
IP Address |
Port Number |
IP Address |
Port Number |
IP Address |
Port Number |
IP Address |
Port Number |
| To Internet |
192.168.1.2 |
1031 |
192.156.136.22 |
1720 |
136.22.36.12 |
1031 |
192.156.136.22 |
1720 |
| From Internet |
192.156.136.22 |
1720 |
136.22.36.12 |
1503 |
192.156.136.22 |
1720 |
192.168.1.2 |
1503 |
The last NAT scenario is the one of an unsolicited incoming
packet. This can happen with online chat / video, where you register
your availability to chat with a "reflector" site. A good example of
the is CU-See Me video conferencing software from White Pine
Software. Once registered, anyone on the internet is free to
communicate with your workstation. If they do, the LAN Modem will
receive an unsolicited packet, and will not know which workstation
to route it to. In this case it will be passed to the workstation
given as the default (under Service Provider configuration).
Q. What is the difference
between a Private Network and an Internet Service
Provider?
A. When configuring a Private Network, you are able to specify
the network address of the remote LAN. When the LAN Modem sees a
packet on the LAN that is destined for an address not on the local
LAN it will look in the Service Provider tables to decide where to
route the packet to.
The LAN Modem first looks though the Private Network entries to
see if the packet matches the specified network address of a remote
LAN. It starts from the first Service Provider profile, and
continues through to the last. If the packet matches the remote
network address, the packet will be routed to that Private Network.
Of course, if there is no data call currently up to that Private
Network, then one will be made.
If there is no match among the Private Network profiles, the LAN
Modem will route a packet to the first Internet Service Provider
entry it finds. In networking terms, the Internet Service Provider
can be considered a "default route".
There are deviations from this logic:
- If a call is already up to a Private Network, and you have
internet access through that network, then the LAN Modem will
route the packet to the Private Network, instead of bringing up a
call to the Internet Service Provider.
- When deciding where to route a packet to, the LAN Modem will
skip over Service Providers that the workstation has been denied
access to. To allow or deny a workstation access to a Service
Provider, click on Workstations and select the workstation
in question. Select the Service Provider(s) that the workstation
had access to.
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