Tahoe 681 User manual

FREEDOM OF COMMUNICATION
USER MANUAL
G.shdsl+ modem with built-in router
TAHOE 681 / 682

i
TABLE OF CONTENTS
1. Introduction ........................................................................ 1
2. Interfaces ........................................................................... 3
3. Modem configuration using built-in keyboard and LCD.5
4. Configuration using telnet or serial console .................... 10
4.1. Telnet connection ............................................................. 10
4.2. Serial console ................................................................. 10
4.3. Commands ...................................................................... 11
5. Technical data .................................................................... 29
6. Declaration of Conformity ................................................. 30

i
TABLE OF CONTENTS
1. Introduction ........................................................................ 1
2. Interfaces ........................................................................... 3
3. Modem configuration using built-in keyboard and LCD.5
4. Configuration using telnet or serial console .................... 10
4.1. Telnet connection ............................................................. 10
4.2. Serial console ................................................................. 10
4.3. Commands ...................................................................... 11
5. Technical data .................................................................... 29
6. Declaration of Conformity ................................................. 30

1
11. Introduction
Thank you for purchasing the Tahoe 681/682 modem. We did our
best to ensure highest reliability and performance of our products.
Devoting many years of research and development we are proud to
provide a superior quality device unfolding new possibilities for the use of
the copper lines.
®
Tahoe 680 series modems are G.shdsl+ modems allowing data
transmission with speeds up to 4864 kbps on 2-wire line or up to 9728
kbps on 4-wire line. Thanks to powerful TCPAM-32 modulation
throughputs are much higher than using HDSL technique and reach is
nearly twice that of VDSL. Adding low cost of deployment, Tahoe
modems become an interesting alternative even for fiber optic
connections.
The modem exists in two versions:
®
¡Tahoe 681 - up to 4864 kbps on 2-wire line
®
¡Tahoe 682 - up to 9728 kbps on 4-wire line, traffic is
automatically divided between two lines, fall back to 2-wire mode
is done automatically in case o line failure
The modem has a built-in TCP/IP router and an Ethernet
10/100Base-T interface allowing connection directly to a LAN. Router
software supports IP, ARP, TCP, UDP and ICMP protocols. It is
manageable using telnet, SNMP, serial console or built-in LCD and
keyboard. Traffic statistics are available through WWW. Modem status
messages can be sent to a central server using syslog protocol.
One network interface may support more than one IP subnetwork
thanks to interface aliases (eth0:0, eth0:1, etc.) and VLAN interfaces
(eth0.1, eth0.2, etc.). Modem may also work as a bridge - in this mode
both interconnected networks create one whole on the hardware level
®
(e.g. computers with Microsoft Windows™ operating system will see
each other in the network neighborhood).
A built-in DHCP/BOOTP server allows assigning of IP addresses,
network mask, router addresses and other parameters to the network
stations. DHCP/BOOTP Relay Agent listens for DHCP and BOOTP
requests and forwards them to a central server.
Modem supports Network Address Translation, i.e. makes it
possible for a whole network to access Internet using only one real IP
address. Additional firewall improves the network security by blocking
ii
®
Tahoe 681/682 (G.shdsl+ / Ethernet 10/100Base-T modem)
User Manual
http://www.tahoe-group.com/
Firmware version 1.2.6
®
©2004 Tahoe . All rights reserved.
Other trademarks of other companies are used only for explanation and to
the owner's benefit, without intent to infringe.
®
Tahoe assumes no responsibility for any errors or omissions that may appear in
®
this document. Tahoe makes no commitment to update the information
contained here, and may make changes at any time without notice.

1
11. Introduction
Thank you for purchasing the Tahoe 681/682 modem. We did our
best to ensure highest reliability and performance of our products.
Devoting many years of research and development we are proud to
provide a superior quality device unfolding new possibilities for the use of
the copper lines.
®
Tahoe 680 series modems are G.shdsl+ modems allowing data
transmission with speeds up to 4864 kbps on 2-wire line or up to 9728
kbps on 4-wire line. Thanks to powerful TCPAM-32 modulation
throughputs are much higher than using HDSL technique and reach is
nearly twice that of VDSL. Adding low cost of deployment, Tahoe
modems become an interesting alternative even for fiber optic
connections.
The modem exists in two versions:
®
¡Tahoe 681 - up to 4864 kbps on 2-wire line
®
¡Tahoe 682 - up to 9728 kbps on 4-wire line, traffic is
automatically divided between two lines, fall back to 2-wire mode
is done automatically in case o line failure
The modem has a built-in TCP/IP router and an Ethernet
10/100Base-T interface allowing connection directly to a LAN. Router
software supports IP, ARP, TCP, UDP and ICMP protocols. It is
manageable using telnet, SNMP, serial console or built-in LCD and
keyboard. Traffic statistics are available through WWW. Modem status
messages can be sent to a central server using syslog protocol.
One network interface may support more than one IP subnetwork
thanks to interface aliases (eth0:0, eth0:1, etc.) and VLAN interfaces
(eth0.1, eth0.2, etc.). Modem may also work as a bridge - in this mode
both interconnected networks create one whole on the hardware level
®
(e.g. computers with Microsoft Windows™ operating system will see
each other in the network neighborhood).
A built-in DHCP/BOOTP server allows assigning of IP addresses,
network mask, router addresses and other parameters to the network
stations. DHCP/BOOTP Relay Agent listens for DHCP and BOOTP
requests and forwards them to a central server.
Modem supports Network Address Translation, i.e. makes it
possible for a whole network to access Internet using only one real IP
address. Additional firewall improves the network security by blocking
ii
®
Tahoe 681/682 (G.shdsl+ / Ethernet 10/100Base-T modem)
User Manual
http://www.tahoe-group.com/
Firmware version 1.2.6
®
©2004 Tahoe . All rights reserved.
Other trademarks of other companies are used only for explanation and to
the owner's benefit, without intent to infringe.
®
Tahoe assumes no responsibility for any errors or omissions that may appear in
®
this document. Tahoe makes no commitment to update the information
contained here, and may make changes at any time without notice.

2
unwanted traffic basing on IP addresses, TCP or UDP ports and protocols
appearing in the received packets.
The system firmware is stored in the Flash memory - it is possible
to update it using the TFTP protocol. The configuration is stored in the
EEPROM memory.
3
2. Interfaces
Following connectors are found on the rear panel of the modem:
2.1. G.shdsl
It is a 6-pin RJ-11 connector used to connect the leased line. In
Tahoe 681 the line should be connected to pins 3 and 4. In case of Tahoe
682 one line should be connected to pins 2 and 3, while the other one - to
pins 4 and 5. The first and second line may be interchanged between
modems - that will be automatically detected. The polarization of a line is
not important.
2.2. Serial console
The RS-232 serial console is used for modem management. It has
a DB9/M connector and works as a DTE, i.e. a null-modem cable should
be used to connect it to a PC. Three lines (bolded) are sufficient. Terminal
settings are 9600 bps, 8 data bits, 1 stop bit, no parity, no handshaking.
2
2.2
Pin Name
1DCD
2
3
4
5
6
RXD
TXD
DTR
GND
DSR
Description
carrier detect, transmission readiness signaling
data received from the PC
data sent by the modem to the PC
active, when the PC is switched on
signal ground
active, when the modem is switched on
7RTS used by the PC to inform that is has data to send
8 CTS used by the modem to permit data transmission
9 RI ring indicator (signal used in telephone modems)
G.shdsl serial
console
LAN
(FastEthernet)
power
switch
power
connector
O
I
2.1
Pin Tahoe 681
1-
2
3
4
5
6
line 1
line 1
line 1
-
Tahoe 682
line 1
line 2
-
line 2
-
-
-

2
unwanted traffic basing on IP addresses, TCP or UDP ports and protocols
appearing in the received packets.
The system firmware is stored in the Flash memory - it is possible
to update it using the TFTP protocol. The configuration is stored in the
EEPROM memory.
3
2. Interfaces
Following connectors are found on the rear panel of the modem:
2.1. G.shdsl
It is a 6-pin RJ-11 connector used to connect the leased line. In
Tahoe 681 the line should be connected to pins 3 and 4. In case of Tahoe
682 one line should be connected to pins 2 and 3, while the other one - to
pins 4 and 5. The first and second line may be interchanged between
modems - that will be automatically detected. The polarization of a line is
not important.
2.2. Serial console
The RS-232 serial console is used for modem management. It has
a DB9/M connector and works as a DTE, i.e. a null-modem cable should
be used to connect it to a PC. Three lines (bolded) are sufficient. Terminal
settings are 9600 bps, 8 data bits, 1 stop bit, no parity, no handshaking.
2
2.2
Pin Name
1DCD
2
3
4
5
6
RXD
TXD
DTR
GND
DSR
Description
carrier detect, transmission readiness signaling
data received from the PC
data sent by the modem to the PC
active, when the PC is switched on
signal ground
active, when the modem is switched on
7RTS used by the PC to inform that is has data to send
8 CTS used by the modem to permit data transmission
9 RI ring indicator (signal used in telephone modems)
G.shdsl serial
console
LAN
(FastEthernet)
power
switch
power
connector
O
I
2.1
Pin Tahoe 681
1-
2
3
4
5
6
line 1
line 1
line 1
-
Tahoe 682
line 1
line 2
-
line 2
-
-
-

4
After connecting the console to the PC and running a terminal
software, user has the same access to the modem functions, as through
a telnet connection (see chapter 4).
2.3. FastEthernet
The FastEthernet interface is used to connect the modem to the
Local Area Network. It may work at speeds of 10 Mbps (10Base-T) or 100
Mbps (100Base-T), in either full-duplex or half-duplex mode. The mode
of transmission is selected automatically.
Modem should be connected to a Ethernet switch or a hub using a
straight patch-cord or to a PC, a router or an uplink port in a switch using
a crossed-over one. After connecting a LED named “LAN Link” should be
lit.
®
In the Tahoe 681/682 modems the FastEthernet interface has
following status LEDs:
¡LAN Link - lit, when modem is connected to a LAN
¡LAN Act - LAN activity, blinks when data is sent or received
¡10/100M - LAN connection throughput - lit, when 100 Mbps
connection speed is negotiated
On the right two WAN status LEDs are present, blinking when data
is, respectively, received from or sent to the DSL line:
¡WAN Rx- WAN Receive
¡WAN Tx - WAN Transmit
5
3. Modem configuration using built-in
keyboard and LCD
The easiest way to configure a modem is to use the four-button
keyboard and the LCD. After switching the power on, an information
about the modem type, the line throughput and state will be displayed.
The messages are different for Tahoe 681 and Tahoe 682 modems:
Four-letter code on the right describes the DSL line state:
¡BOOT - booting of the G.shdsl transceiver
¡IDLE - transceiver inactive
¡DOWN - transceiver active, line not synchronized
¡SYNC - line synchronized, data may be transmitted
In case of Tahoe 682 modem, the top code describes the first
line, while the bottom - the second one.
On the right of the display there is a keyboard with “up”, “down”,
“Escape” and “Enter” keys. By pressing up/down buttons you may
browse the configuration menu:
¡speed setting
¡modem type setting (Master/Slave)
¡line modulation selection
¡storing settings in the EEPROM memory
¡setting the IP address and network mask on the eth0 interface
¡selection of the language
¡connection reset
¡modem reset
¡bridge mode toggling
Each pressing of the “Escape” button causes the return to the
primary display with modem type and state. Pressing of the “Enter”
button selects given menu option.
Tahoe 681
4864 kb/s BOOT
Tahoe 682 BOOT
9728 kb/s BOOT
2.3
3

4
After connecting the console to the PC and running a terminal
software, user has the same access to the modem functions, as through
a telnet connection (see chapter 4).
2.3. FastEthernet
The FastEthernet interface is used to connect the modem to the
Local Area Network. It may work at speeds of 10 Mbps (10Base-T) or 100
Mbps (100Base-T), in either full-duplex or half-duplex mode. The mode
of transmission is selected automatically.
Modem should be connected to a Ethernet switch or a hub using a
straight patch-cord or to a PC, a router or an uplink port in a switch using
a crossed-over one. After connecting a LED named “LAN Link” should be
lit.
®
In the Tahoe 681/682 modems the FastEthernet interface has
following status LEDs:
¡LAN Link - lit, when modem is connected to a LAN
¡LAN Act - LAN activity, blinks when data is sent or received
¡10/100M - LAN connection throughput - lit, when 100 Mbps
connection speed is negotiated
On the right two WAN status LEDs are present, blinking when data
is, respectively, received from or sent to the DSL line:
¡WAN Rx- WAN Receive
¡WAN Tx - WAN Transmit
5
3. Modem configuration using built-in
keyboard and LCD
The easiest way to configure a modem is to use the four-button
keyboard and the LCD. After switching the power on, an information
about the modem type, the line throughput and state will be displayed.
The messages are different for Tahoe 681 and Tahoe 682 modems:
Four-letter code on the right describes the DSL line state:
¡BOOT - booting of the G.shdsl transceiver
¡IDLE - transceiver inactive
¡DOWN - transceiver active, line not synchronized
¡SYNC - line synchronized, data may be transmitted
In case of Tahoe 682 modem, the top code describes the first
line, while the bottom - the second one.
On the right of the display there is a keyboard with “up”, “down”,
“Escape” and “Enter” keys. By pressing up/down buttons you may
browse the configuration menu:
¡speed setting
¡modem type setting (Master/Slave)
¡line modulation selection
¡storing settings in the EEPROM memory
¡setting the IP address and network mask on the eth0 interface
¡selection of the language
¡connection reset
¡modem reset
¡bridge mode toggling
Each pressing of the “Escape” button causes the return to the
primary display with modem type and state. Pressing of the “Enter”
button selects given menu option.
Tahoe 681
4864 kb/s BOOT
Tahoe 682 BOOT
9728 kb/s BOOT
2.3
3

6
3.1. Throughput setting
After pressing Enter the throughput may be set using up/down
buttons. In Tahoe 681 modem it may be chosen from 64-4864 kbps
range with 64 kbps step, while in Tahoe 682 - from 128-9728 kbps
range with 128 kbps step. In the latter case the actual throughput of
each line is half of the throughput set. Different rates for each line may
be set using the serial console or the telnet connection (see chapter 4).
After choosing the right speed and pressing Enter modem will
reset the connection and renegotiate it with new settings.
NOTE: The same throughput must be set on both modems.
3.2. Modem type
After pressing Enter the modem type may be selected - either
Master (HTU-C) or Slave (HTU-R). After selecting the type and pressing
Enter again the connection will be reset and renegotiated with new
settings.
NOTE: Always one modem has to be set as a Master and the
other one as a Slave.
3.3. Line coding
After pressing Enter the G.shdsl line coding (signal modulation)
may be chosen. The number (32 in the example above) means the
number of values encoded in one symbol (32 - 5 bits per symbol). The
higher this number is, the lower is the signal frequency, which gives
better immunity for signal attenuation and higher reach.
The second part - PAM or TCPAM - means either the Pulse
Amplitude Modulation or Trellis Coded Pulse Amplitude Modulation.
The latter is more efficient.
It is recommended to use the 32-TCPAM modulation, which
provides the best results. The remaining line codings are available to
provide compatibility with others’ manufacturers equipment. Moreover
32-TCPAM allows throughputs from 256 kbps to 4864 kbps per line,
while 16-TCPAM - from 64 kbps to 2304 kbps.
The “Auto” setting forces use of 32-TCPAM for speeds higher
than or equal to 256 kbps per line and 16-TCPAM for lower rates.
3.4. Write configuration to EEPROM
Every change to the configuration will be lost after reboot or
power off unless the settings are written to the EEPROM. After reaching
this option just press Enter to save them.
3.5. IP address and network mask on eth0 interface
As a factory default the Ethernet interface of the modem has the
IP address set to 10.0.0.1 and the network mask to 255.0.0.0. After
connecting to this address using telnet further configuration can be
done. The IP address may be changed, however, using the keyboard.
It’s useful when the IP address has been changed and then forgotten.
After pressing Enter, up and down buttons may be used to
change the first octet of the IP address:
Then after pressing Enter second, third and fourth octet may be
set. Afterwards the network mask may be changed. Up and down keys
lengthen or shorten it, respectively, by one bit:
7
Write config
to EEPROM
Line coding:
32-TCPAM
3.1
3.2
Modem type:
Master / HTU-C
Line rate:
9728 kb/s
IP address and
netmask on eth0
3.4
3.5
Set IP address:
10._._._
Set netmask:
255.0.0.0
3.3

6
3.1. Throughput setting
After pressing Enter the throughput may be set using up/down
buttons. In Tahoe 681 modem it may be chosen from 64-4864 kbps
range with 64 kbps step, while in Tahoe 682 - from 128-9728 kbps
range with 128 kbps step. In the latter case the actual throughput of
each line is half of the throughput set. Different rates for each line may
be set using the serial console or the telnet connection (see chapter 4).
After choosing the right speed and pressing Enter modem will
reset the connection and renegotiate it with new settings.
NOTE: The same throughput must be set on both modems.
3.2. Modem type
After pressing Enter the modem type may be selected - either
Master (HTU-C) or Slave (HTU-R). After selecting the type and pressing
Enter again the connection will be reset and renegotiated with new
settings.
NOTE: Always one modem has to be set as a Master and the
other one as a Slave.
3.3. Line coding
After pressing Enter the G.shdsl line coding (signal modulation)
may be chosen. The number (32 in the example above) means the
number of values encoded in one symbol (32 - 5 bits per symbol). The
higher this number is, the lower is the signal frequency, which gives
better immunity for signal attenuation and higher reach.
The second part - PAM or TCPAM - means either the Pulse
Amplitude Modulation or Trellis Coded Pulse Amplitude Modulation.
The latter is more efficient.
It is recommended to use the 32-TCPAM modulation, which
provides the best results. The remaining line codings are available to
provide compatibility with others’ manufacturers equipment. Moreover
32-TCPAM allows throughputs from 256 kbps to 4864 kbps per line,
while 16-TCPAM - from 64 kbps to 2304 kbps.
The “Auto” setting forces use of 32-TCPAM for speeds higher
than or equal to 256 kbps per line and 16-TCPAM for lower rates.
3.4. Write configuration to EEPROM
Every change to the configuration will be lost after reboot or
power off unless the settings are written to the EEPROM. After reaching
this option just press Enter to save them.
3.5. IP address and network mask on eth0 interface
As a factory default the Ethernet interface of the modem has the
IP address set to 10.0.0.1 and the network mask to 255.0.0.0. After
connecting to this address using telnet further configuration can be
done. The IP address may be changed, however, using the keyboard.
It’s useful when the IP address has been changed and then forgotten.
After pressing Enter, up and down buttons may be used to
change the first octet of the IP address:
Then after pressing Enter second, third and fourth octet may be
set. Afterwards the network mask may be changed. Up and down keys
lengthen or shorten it, respectively, by one bit:
7
Write config
to EEPROM
Line coding:
32-TCPAM
3.1
3.2
Modem type:
Master / HTU-C
Line rate:
9728 kb/s
IP address and
netmask on eth0
3.4
3.5
Set IP address:
10._._._
Set netmask:
255.0.0.0
3.3

8
Press Enter again to approve new settings or Escape to cancel
the operation.
3.6. Language selection
After pressing Enter the language used on LCD and during the
telnet connection may be changed.
3.7. Connection reset
After pressing Enter the G.shdsl link will be disconnected and
negotiated again.
3.8. Modem reset
After pressing Enter the whole modem is rebooted. If some
settings were not saved to the EEPROM, they will be lost.
3.9. Bridge mode
This option enables or disables the bridge mode, in which two
interconnected LANs create one whole in the hardware layer. Three
settings are available:
¡off - regular TCP/IP routing
¡on - bridge enabled, but the modem is still available under its IP
address and thus may be managed remotely
¡transparent - completely transparent bridge
9
3.10. Line parameters
The “Esc” button returns to the main screen (with modem type,
throughput and link state). While having this screen displayed, you
may press Enter to display line attenuation in dB (proper value appears
only after the line synchronizes):
In case of the two-pair modem - Tahoe 682 - both lines
attenuations are shown:
Pressing Enter again will show so-called Noise Margin (or Signal-
Noise Ratio). This is the difference between the useful signal and the
background noise. It may be used to estimate, how much the line rate
may be increased without causing any problems with the
synchronization.
When the NMR is less than 0 dB modems will be unable to bring
the link up.
It is the best practice to keep the NMR equal to or higher than 5
dB, so the error rate will be unnoticeable. Otherwise the packets will be
lost due to bit errors and the retransmission would be necessary, thus
decreasing the overall effective throughput.
This parameter is also valid only when the lines are fully
synchronized. In case of Tahoe 682 modem both lines NMRs are
shown:
Pressing Enter again will return to the main screen with the
throughput and modem state.
3.7
3.10
3.6
Bridge:
on
Connection reset
(press Enter)
Modem reset
(press Enter)
Line attenuation:
12.5 dB
Noise margin:
6.0 dB
Line attenuation:
12.5 / 12.0 dB
3.8
Noise margin:
5.0 / 5.0 dB
Language:
English
3.9

8
Press Enter again to approve new settings or Escape to cancel
the operation.
3.6. Language selection
After pressing Enter the language used on LCD and during the
telnet connection may be changed.
3.7. Connection reset
After pressing Enter the G.shdsl link will be disconnected and
negotiated again.
3.8. Modem reset
After pressing Enter the whole modem is rebooted. If some
settings were not saved to the EEPROM, they will be lost.
3.9. Bridge mode
This option enables or disables the bridge mode, in which two
interconnected LANs create one whole in the hardware layer. Three
settings are available:
¡off - regular TCP/IP routing
¡on - bridge enabled, but the modem is still available under its IP
address and thus may be managed remotely
¡transparent - completely transparent bridge
9
3.10. Line parameters
The “Esc” button returns to the main screen (with modem type,
throughput and link state). While having this screen displayed, you
may press Enter to display line attenuation in dB (proper value appears
only after the line synchronizes):
In case of the two-pair modem - Tahoe 682 - both lines
attenuations are shown:
Pressing Enter again will show so-called Noise Margin (or Signal-
Noise Ratio). This is the difference between the useful signal and the
background noise. It may be used to estimate, how much the line rate
may be increased without causing any problems with the
synchronization.
When the NMR is less than 0 dB modems will be unable to bring
the link up.
It is the best practice to keep the NMR equal to or higher than 5
dB, so the error rate will be unnoticeable. Otherwise the packets will be
lost due to bit errors and the retransmission would be necessary, thus
decreasing the overall effective throughput.
This parameter is also valid only when the lines are fully
synchronized. In case of Tahoe 682 modem both lines NMRs are
shown:
Pressing Enter again will return to the main screen with the
throughput and modem state.
3.7
3.10
3.6
Bridge:
on
Connection reset
(press Enter)
Modem reset
(press Enter)
Line attenuation:
12.5 dB
Noise margin:
6.0 dB
Line attenuation:
12.5 / 12.0 dB
3.8
Noise margin:
5.0 / 5.0 dB
Language:
English
3.9

10
4. Modem configuration using telnet or
serial console
4.1. Telnet connection
To connect to the modem the network interface in your PC has to
be in the same IP subnet as the modem. By default the modem’s
Ethernet interface is set to 10.0.0.1 address and 255.0.0.0 netmask, so
the PC may have IP address set to 10.0.0.2 and the same netmask.
If the modem was already configured and the routing table is
correctly set up, a telnet connection to its IP address is possible from
anywhere in the network.
After connecting a password prompt will appear:
User Access Verification
Password:
The default password is “Tahoe” (case sensitive). If the
password entered is correct, a command prompt will appear:
Tahoe>
4.2. Serial console
If the telnet connection is not possible (e.g. there’s no telnet client
available or the modem’s IP address is unknown), the modem may be
connected to the PC’s serial port using a null-modem cable. After starting
a terminal software (e.g. minicom under Linux operating system,
®
Hyperterm under Microsoft Windows™) user gets the same access as
through the telnet connection. After pressing Enter the same command
prompt appears:
Tahoe>
By default the console access isn’t password protected, but such
protection may be enabled later using “console password” command.
11
4.3. Commands
4.3.1. ?, help
Entering “?” or “help” shows a list of available commands.
4.3.2. arp
The “arp” command is used to configure the ARP table. The “arp”
alone shows the list of connections between IP and hardware (MAC)
addresses:
Tahoe> arp
IP address Hardware address
10.0.0.2 00:50:04:0D:70:31 dynamic
ARP table entries may be deleted using “arp del”:
Tahoe> arp del 10.0.0.2
(the IP address to be deleted should be typed instead of
“10.0.0.2” ).
A static ARP entry may be added using “arp add”:
Tahoe> arp add 10.0.0.3 00:50:13:E9:5C:01
The dynamic hardware address resolution may be disabled using
the “ifconfig” command. If it is disabled, only those stations may connect
to the modem, whose IP and MAC addresses are entered into the ARP
table using the “arp add” command. This way an unauthorized network
access may be prohibited.
4.3.3. bridge
The “bridge” command enables or disables the bridge mode, in
which two interconnected LANs create one whole in the hardware layer.
The stations in both LANs behave like if they were connected to one
®
Ethernet switch, e.g. PCs working under Microsoft Windows™
operating system will see each other in the network neighborhood.
Three settings are available:
¡off - regular TCP/IP routing
¡on - bridge enabled, but the modem is still available under its IP
address and thus may be managed remotely
4.1
4.2
44.3
4.3.2
4.3.1
4.3.3

10
4. Modem configuration using telnet or
serial console
4.1. Telnet connection
To connect to the modem the network interface in your PC has to
be in the same IP subnet as the modem. By default the modem’s
Ethernet interface is set to 10.0.0.1 address and 255.0.0.0 netmask, so
the PC may have IP address set to 10.0.0.2 and the same netmask.
If the modem was already configured and the routing table is
correctly set up, a telnet connection to its IP address is possible from
anywhere in the network.
After connecting a password prompt will appear:
User Access Verification
Password:
The default password is “Tahoe” (case sensitive). If the
password entered is correct, a command prompt will appear:
Tahoe>
4.2. Serial console
If the telnet connection is not possible (e.g. there’s no telnet client
available or the modem’s IP address is unknown), the modem may be
connected to the PC’s serial port using a null-modem cable. After starting
a terminal software (e.g. minicom under Linux operating system,
®
Hyperterm under Microsoft Windows™) user gets the same access as
through the telnet connection. After pressing Enter the same command
prompt appears:
Tahoe>
By default the console access isn’t password protected, but such
protection may be enabled later using “console password” command.
11
4.3. Commands
4.3.1. ?, help
Entering “?” or “help” shows a list of available commands.
4.3.2. arp
The “arp” command is used to configure the ARP table. The “arp”
alone shows the list of connections between IP and hardware (MAC)
addresses:
Tahoe> arp
IP address Hardware address
10.0.0.2 00:50:04:0D:70:31 dynamic
ARP table entries may be deleted using “arp del”:
Tahoe> arp del 10.0.0.2
(the IP address to be deleted should be typed instead of
“10.0.0.2” ).
A static ARP entry may be added using “arp add”:
Tahoe> arp add 10.0.0.3 00:50:13:E9:5C:01
The dynamic hardware address resolution may be disabled using
the “ifconfig” command. If it is disabled, only those stations may connect
to the modem, whose IP and MAC addresses are entered into the ARP
table using the “arp add” command. This way an unauthorized network
access may be prohibited.
4.3.3. bridge
The “bridge” command enables or disables the bridge mode, in
which two interconnected LANs create one whole in the hardware layer.
The stations in both LANs behave like if they were connected to one
®
Ethernet switch, e.g. PCs working under Microsoft Windows™
operating system will see each other in the network neighborhood.
Three settings are available:
¡off - regular TCP/IP routing
¡on - bridge enabled, but the modem is still available under its IP
address and thus may be managed remotely
4.1
4.2
44.3
4.3.2
4.3.1
4.3.3

12
¡transparent - completely transparent bridge, inaccessible under
its IP address - this mode may be disabled only through the serial
console or the LCD and keyboard.
Entering “bridge list” displays a list of MAC addresses with the
name of the interface on which certain address was heard.
Note: To make bridging work properly interfaces used in the process
have to be indicated. To enable bridging on a certain interface
enter “ifconfig <interface name> bridge on”.
®
Note: To enable bridging the Cisco HDLC link protocol should also be
selected using “dsl hdlc” command
4.3.4. con
The „con” command erases whole configuration from the
EEPROM. After rebooting the modem it will return to its factory defaults.
Until the reboot it will continue to run with its current settings, which can
be saved again using “write” command.
4.3.5. config
The „config” command displays current configuration. The
command output may be entered on another modem to make an exact
copy of the configuration.
4.3.6. console
This command is used to enable or disable password the
protection of the serial console. By default the console is unprotected
and user has full access to the modem. By entering:
console passwd on
the password requirement is enabled and modem will ask for it in the
same manner as during the telnet connection. To disable password
protection type:
console passwd off
4.3.7. dhcp
The “dhcp” command is used to configure DHCP/BOOTP server
and relay agent. The server is used to assign IP addresses, network
masks, gateway and DNS addresses and other parameters to the
13
network stations. It is easy to reconfigure a network that uses a DHCP
server - it is enough to change server settings and every station will
automatically retrieve new configuration.
The BOOTP protocol is an earlier and simpler version of DHCP. Its
common use is booting of diskless workstations. A workstation uses
BOOTP to get its IP address and other network parameters together with
TFTP server address, from which the operating system may be
downloaded.
The DHCP protocol may deliver more working parameters
including domain name, DNS address, print server, syslog server, X-
Window fontserver, MTU and TTL settings, and many others.
DHCP/BOOTP Relay Agent transfers DHCP and BOOTP requests
and replies between separate networks. The DHCP and BOOTP protocols
work only within one physical subnet. The station using such protocols
doesn’t know its IP address yet, so its packets cannot be routed to other
networks. Relay Agent listens for such requests and forwards them to a
DHCP server, which may be placed anywhere in the network.
4.3.7.1. Review of the settings
Entering “dhcp” alone displays current server settings. Here is an
example:
Tahoe> dhcp
DHCP/BOOTP server
default-lease-time 43200
max-lease-time 86400
network "lan" (eth0):
default-lease-time 43200
max-lease-time 86400
domain-name tahoe.pl
subnet "local": 10.0.0.0/255.255.255.0
default-lease-time 43200
max-lease-time 86400
filename vmlinuz.2.2.19
next-server 192.168.0.5
routers 10.0.0.1
domain-name-servers 192.168.0.4
domain-name tahoe.pl
address ranges: 10.0.0.3-10.0.0.15
relay server 192.168.0.5 67
4.3.6
4.3.5
4.3.4
4.3.7
4.3.7.1

12
¡transparent - completely transparent bridge, inaccessible under
its IP address - this mode may be disabled only through the serial
console or the LCD and keyboard.
Entering “bridge list” displays a list of MAC addresses with the
name of the interface on which certain address was heard.
Note: To make bridging work properly interfaces used in the process
have to be indicated. To enable bridging on a certain interface
enter “ifconfig <interface name> bridge on”.
®
Note: To enable bridging the Cisco HDLC link protocol should also be
selected using “dsl hdlc” command
4.3.4. con
The „con” command erases whole configuration from the
EEPROM. After rebooting the modem it will return to its factory defaults.
Until the reboot it will continue to run with its current settings, which can
be saved again using “write” command.
4.3.5. config
The „config” command displays current configuration. The
command output may be entered on another modem to make an exact
copy of the configuration.
4.3.6. console
This command is used to enable or disable password the
protection of the serial console. By default the console is unprotected
and user has full access to the modem. By entering:
console passwd on
the password requirement is enabled and modem will ask for it in the
same manner as during the telnet connection. To disable password
protection type:
console passwd off
4.3.7. dhcp
The “dhcp” command is used to configure DHCP/BOOTP server
and relay agent. The server is used to assign IP addresses, network
masks, gateway and DNS addresses and other parameters to the
13
network stations. It is easy to reconfigure a network that uses a DHCP
server - it is enough to change server settings and every station will
automatically retrieve new configuration.
The BOOTP protocol is an earlier and simpler version of DHCP. Its
common use is booting of diskless workstations. A workstation uses
BOOTP to get its IP address and other network parameters together with
TFTP server address, from which the operating system may be
downloaded.
The DHCP protocol may deliver more working parameters
including domain name, DNS address, print server, syslog server, X-
Window fontserver, MTU and TTL settings, and many others.
DHCP/BOOTP Relay Agent transfers DHCP and BOOTP requests
and replies between separate networks. The DHCP and BOOTP protocols
work only within one physical subnet. The station using such protocols
doesn’t know its IP address yet, so its packets cannot be routed to other
networks. Relay Agent listens for such requests and forwards them to a
DHCP server, which may be placed anywhere in the network.
4.3.7.1. Review of the settings
Entering “dhcp” alone displays current server settings. Here is an
example:
Tahoe> dhcp
DHCP/BOOTP server
default-lease-time 43200
max-lease-time 86400
network "lan" (eth0):
default-lease-time 43200
max-lease-time 86400
domain-name tahoe.pl
subnet "local": 10.0.0.0/255.255.255.0
default-lease-time 43200
max-lease-time 86400
filename vmlinuz.2.2.19
next-server 192.168.0.5
routers 10.0.0.1
domain-name-servers 192.168.0.4
domain-name tahoe.pl
address ranges: 10.0.0.3-10.0.0.15
relay server 192.168.0.5 67
4.3.6
4.3.5
4.3.4
4.3.7
4.3.7.1

14
4.3.7.2. Basic DHCP server configuration rules
Before starting using DHCP server please read following
guidelines:
¡the configuration is organized in a hierarchical manner - the most
general group of settings is “network” - the physical network
connected to the modem. Any number of IP “subnets” may exist
within a network. Inside an IP subnet an IP address “range” may
be selected - these addresses will be dynamically assigned to the
network stations. A static connection between an IP address and a
hardware address may also be set. Each group (“network”,
“subnet”) has its own options. Creating a new group (e.g. a
“subnet” within a “network”) causes copying of the options from
the parent group (e.g. if the “lan” network has a “domain-name”
option, after adding a “local” subnet within “lan” the option will be
automatically copied - it may be modified or deleted later)
¡on the beginning a “network” for each interface should be created
¡in each of the “networks” an IP “subnet” should be created
according to IP subnets connected to that interface (modem may
not have the routing set up to each of them - it’s enough that they
are in the same physical network)
¡now IP ranges and static IP entries may be added
4.3.7.3. dhcp [ on | off | relay ]
DHCP/BOOTP server may work in one of three modes:
¡on - the server in enabled and answers to the requests
¡off - the server is disabled
¡relay - the server is disabled, but the relay agent is enabled and
listens for the requests to be forwarded to other DHCP server
4.3.7.4. dhcp add
The “dhcp add” commands add a network, subnet, IP range, etc.
Following variants are supported:
¡dhcp add network <name>
Adds a new physical network connected to the modem’s interface.
There should be the same number of “networks” and interfaces. The
“network”-interface connection will be determined later while adding the
IP subnets.
15
dhcp add network lan
¡dhcp add subnet <name> <network> <address>
<netmask>
Adds a net IP subnet to a given network. For each IP subnet
connected to the LAN or WAN interface an DHCP subnet should be added
(with the same IP addresses, as configured on each of the interfaces).
Moreover additional IP subnets may be added - those which are not set
up on any of the interfaces, but do exist in the same physical network or
behind a DHCP relay:
dhcp add subnet local lan 10.0.0.0 255.0.0.0
¡dhcp add host <name> <MAC address> <IP address>
Adds a static connection between hardware (MAC) and IP
addresses. The IP address must belong to one of the configured subnets.
Only this IP address will be assigned to the given MAC address:
dhcp add host server 00:50:13:2e:15:ca 10.0.0.5
¡dhcp add range <start address> <end address>
Adds an IP address range, from which addresses will be assigned
to the network stations. The address range must be contained inside one
of the subnets:
dhcp add range 10.0.0.5 10.0.0.37
¡dhcp add option <option> <value>
Adds a global DHCP option sent to the requesting station.
Available options are:
-routers - network gateways (usually the gateways should be
separate for each subnet, so they shouldn’t be defined globally)
-domain-name - domain name
-domain-name-servers - DNS addresses
-filename - name of the file containing the operating system
-next-server - server from which the mentioned above file will
be downloaded using TFTP
dhcp add option domain-name tahoe-group.com
4.3.7.4
4.3.7.3
4.3.7.2

14
4.3.7.2. Basic DHCP server configuration rules
Before starting using DHCP server please read following
guidelines:
¡the configuration is organized in a hierarchical manner - the most
general group of settings is “network” - the physical network
connected to the modem. Any number of IP “subnets” may exist
within a network. Inside an IP subnet an IP address “range” may
be selected - these addresses will be dynamically assigned to the
network stations. A static connection between an IP address and a
hardware address may also be set. Each group (“network”,
“subnet”) has its own options. Creating a new group (e.g. a
“subnet” within a “network”) causes copying of the options from
the parent group (e.g. if the “lan” network has a “domain-name”
option, after adding a “local” subnet within “lan” the option will be
automatically copied - it may be modified or deleted later)
¡on the beginning a “network” for each interface should be created
¡in each of the “networks” an IP “subnet” should be created
according to IP subnets connected to that interface (modem may
not have the routing set up to each of them - it’s enough that they
are in the same physical network)
¡now IP ranges and static IP entries may be added
4.3.7.3. dhcp [ on | off | relay ]
DHCP/BOOTP server may work in one of three modes:
¡on - the server in enabled and answers to the requests
¡off - the server is disabled
¡relay - the server is disabled, but the relay agent is enabled and
listens for the requests to be forwarded to other DHCP server
4.3.7.4. dhcp add
The “dhcp add” commands add a network, subnet, IP range, etc.
Following variants are supported:
¡dhcp add network <name>
Adds a new physical network connected to the modem’s interface.
There should be the same number of “networks” and interfaces. The
“network”-interface connection will be determined later while adding the
IP subnets.
15
dhcp add network lan
¡dhcp add subnet <name> <network> <address>
<netmask>
Adds a net IP subnet to a given network. For each IP subnet
connected to the LAN or WAN interface an DHCP subnet should be added
(with the same IP addresses, as configured on each of the interfaces).
Moreover additional IP subnets may be added - those which are not set
up on any of the interfaces, but do exist in the same physical network or
behind a DHCP relay:
dhcp add subnet local lan 10.0.0.0 255.0.0.0
¡dhcp add host <name> <MAC address> <IP address>
Adds a static connection between hardware (MAC) and IP
addresses. The IP address must belong to one of the configured subnets.
Only this IP address will be assigned to the given MAC address:
dhcp add host server 00:50:13:2e:15:ca 10.0.0.5
¡dhcp add range <start address> <end address>
Adds an IP address range, from which addresses will be assigned
to the network stations. The address range must be contained inside one
of the subnets:
dhcp add range 10.0.0.5 10.0.0.37
¡dhcp add option <option> <value>
Adds a global DHCP option sent to the requesting station.
Available options are:
-routers - network gateways (usually the gateways should be
separate for each subnet, so they shouldn’t be defined globally)
-domain-name - domain name
-domain-name-servers - DNS addresses
-filename - name of the file containing the operating system
-next-server - server from which the mentioned above file will
be downloaded using TFTP
dhcp add option domain-name tahoe-group.com
4.3.7.4
4.3.7.3
4.3.7.2

16
¡dhcp add relay <address> [<port>]
Adds a DHCP server address to which the DHCP requests are
forwarded, when the Relay Agent mode is enabled. The <port>
parameter is optional - its default value is 67:
dhcp add relay 192.168.0.3
4.3.7.5. dhcp del
The command deletes a network, subnet, address range, etc.
¡dhcp del network <name>
¡dhcp del subnet <name>
¡dhcp del host <name>
The commands above delete, respectively, a network, an IP
subnet or a host (a static IP-MAC connection) with given name.
¡dhcp del relay <address>
Deletes a DHCP server address used in the Relay Agent mode.
¡dhcp del range <start address> <end address>
Deletes an IP address range assigned to the network stations.
¡dhcp del option <name> <value>
Deletes a global option. Besides the option name, its value should
also be given, because some options may have more than one value
(e.g. domain name servers, routers, etc.).
4.3.7.6. dhcp rename
The command changes the name of a network, subnet or host:
¡dhcp rename network <old name> <new name>
¡dhcp rename subnet <old name> <new name>
¡dhcp rename host <old name> <new name>
4.3.7.7. dhcp network/subnet/host
The command adds or deletes an option within a specified group -
network, subnet or host. It has two forms:
17
¡dhcp network add <option name> <value>
¡dhcp network del <option name> <value>
(instead of „network”, a „subnet” or „host” may be given; options
are described in 4.3.7.4), e.g. :
dhcp network add domain-name tahoe-group.com
Options are valid only for a given network, subnet or host.
Moreover two other parameters can be set:
¡dhcp network default-lease-time <value>
Sets the time (in second), for which the IP address is assigned to
the station. After that time the station must inform the DHCP server that
it still uses that address. Otherwise the address will be considered as
unused. This timeout prevents blocking an IP address when a station is
switched off without releasing that address.
¡dhcp network max-lease-time <value>
A station may request other lease time - the negotiated time may
not be higher than this setting.
4.3.7.8. dhcp default-lease-time <value>
dhcp max-lease-time <value>
These commands are similar to those described in the previous
paragraph, but their meaning is global.
4.3.8. dsl
This is a group of commands used to configure the DSL link.
Following options are available:
¡dsl { fr | ppp | hdlc } - selects the protocol used to send data
®
through the line - Frame Relay, synchronous PPP or Cisco HDLC.
®
The Cisco HDLC is recommended if the modem has to work in
the bridge mode.
¡dsl speed <value> [<second line>] - sets the line
throughput.
In case of Tahoe 681 modem the value should be selected from
64-4864 kbps range with 64 kbps step.
In Tahoe 682 modems the throughput may be set in two ways -
either by giving the total rate from 128-9728 kbps range, or by
4.3.7.6
4.3.7.8
4.3.8
4.3.7.5
4.3.7.7