User manual
Table Of Contents
- Table of Contents
- About This Guide
- Introduction
- ISDN LAN Modem Functionality Description
- Hardware Description and Installation
- Setting Up TCP/IP for Windows and Macintosh
- Configuring the ISDN LAN Modem
- Advanced Configuration
- Before you Begin
- Setting Up Additional Service Providers
- Editing Service Provider Profiles
- Restricting Workstations from Accessing Service Provider(s)
- Configuring Your LAN Parameters
- Changing Data Call Parameters
- Changing Voice Call Routing
- Reserving DHCP Addresses
- Selective Password Protection
- Changing Your Password
- Setting Up Your ISDN Line Manually
- Locking and Unlocking the Configuration
- Configuring the ISDN LAN Modem from a Remote Location
- Supplementary Voice Call Services
- Placing, Receiving and Disconnecting Calls
- Troubleshooting and Maintenance
- Networking Primer
- What is a network?
- What is a LAN?
- What is a WAN?
- How does a LAN connect to a WAN?
- What is a LAN modem?
- What is ISDN?
- How do different devices communicate with each other?
- What is TCP/IP?
- What is an IP Address?
- What is a Subnet Mask?
- Dynamic and Static IP Addresses
- What is DHCP?
- What is DNS?
- What is NAT?
- What are numbered and unnumbered links?
- How is overall throughput determined?
- What is a network?
- Using the Custom Web Browser
- ISDN LAN Modem Factory Defaults
- ISDN LAN Modem Specifications
- Ordering ISDN Service
- If You Place Your ISDN Order Through 3Com
- If You Place Your ISDN Order Through the Telephone Company
- Supplementary Voice Features Included with U, EZ-ISDN-1, V and EZ-ISDN 1A
- Limitations of ISDN Ordering Codes U, EZ-ISDN 1, V and EZ-ISDN 1A
- What If I Already Have ISDN Service?
- Table of ISDN Ordering Code Capabilities
- Glossary
- Index
- 3Com Corporation Limited Warranty

Evaluating Symptoms and Solutions 97
May be an incompatibility with
the router into which you are
dialing. Some remote routers split
the two B channels of a Multilink
PPP call between different
routing devices, preventing the
channels from being linked.
Try reconnecting your call during off peak hours. If you
are still unable to establish a Multilink PPP call, contact
your ISP to confirm that they support this feature.
A Multilink PPP call was
established but did not remain
connected.
When the LAN Modem is
configured to Use 2 B channels
and the remote end disconnects
one of the 2 B channels, the LAN
Modem will disconnect the now
single B channel call since it’s
configured to use 2 B channels.
From the ISDN LAN Modem’s home page, click Service
Providers and then select the provider you were
connecting to using Multilink PPP. For Bandwidth
Allocation, select Add second B channel as required.
A voice or data call may already
be connected leaving only one
B channel available.
Place the Multilink PPP call when both B channels are
available.
Although only one data call is
connected, another voice or
data call cannot be placed.
The connected call may be
configured to always use two
B channels, leaving no bandwidth
available for another call.
Check the bandwidth allocation setting for that service
provider. Refer to “Editing Service Provider Profiles” in
Chapter 6 for details.
Caller ID date and time are not
accurate.
Connect a workstation that has the correct time to the
ISDN LAN Modem and then turn the LAN Modem
power off and then on again. Once it is powered up,
launch your web browser and go to the LAN Modem's
main page at http://3Com.oc.lanmodem/
Cannot place a call over the
LAN Modem's phone port
using a Sportster PC Card
modem.
Modem mistakes analog phone
line for digital line.
Add the following command to the Sportster modem
init string: AT ~~L0.
Cannot place or receive two
simultaneous voice calls.
Your ISDN line may not support
simultaneous voice and data on
both B channels.
Check with your ISDN line provider to determine
whether or not your ISDN line supports simultaneous
voice and data on both B channels.
For a Lucent 5ESS switch, your ISDN line must have
Max B Channel Limit=2 for simultaneous voice and
data.
For a Siemens switch, your ISDN line must have
Number of B Channels Per Call Type Per Office
Equipment Directory Number (NBCCTOEDN) =2.
After placing a Multilink PPP
call, you lift the handset of a
telephone to place a call and
do not hear a dial tone.
The handset was lifted to place a
call while the ISDN LAN Modem
was negotiating the Multilink PPP
call. Negotiation must be
complete before a call can be
placed.
Hang up the handset, wait a few seconds, and then try
again.
Not receiving message
indication for Voice Mail or any
voice mail messages.
Message Service box is not
checked.
From the ISDN LAN Modem’s main configuration page,
click ISDN Parameters. Under Supplementary Services,
check the box labeled Message Service.
Cannot hear dial tone when
attempting to place a call using
an ISDN LAN Modem phone
port.
Bandwidth Allocation may be set
to Use two B Channels.
Go to the appropriate Service Providers page and
change the Bandwidth Allocations setting to Add
second B channel as required.
(continued)
Table 6
Symptoms, Causes, and Solutions
Symptom Possible Cause Solution