Using Synchronous V.25bis Connections        15

This chapter discusses the following topics:

•  "Overview of Synchronous V.25bis Dial-Up Connections" on page 14-1

•  "Configuration Steps for a Synchronous V.25bis Connection" on page 14-3

•  "Troubleshooting a Synchronous V.25bis Connection" on page 14-13

  See the Command Line Administrator's Guide for more detailed command descriptions and instructions.

Overview of Synchronous V.25bis Dial-Up Connections

Switched 56Kbps connections require an external CSU/DSU. ISDN and switched 56Kbps connections can be initiated on an as-needed basis or they can remain active all the time. A dial-out location must be specified in the location table for dial-out connections, and a dial-in user must be specified in the user table for dial-in connections. PAP is available for dial-in authentication, when a router dials in to your PortMaster. CHAP is available for dial-in and dial-out authentication.

When connecting an asynchronous ISDN terminal adapter to an asynchronous port using AT commands to dial, configure the PortMaster just as you would for a modem. Refer to Chapter 15, "Using Office-to-Office Connections," and Chapter 16, "Using Internet Connections," for more information.

In this configuration, keep in mind that a 115.2Kbps asynchronous DTE rate can support only a single 64Kbps B channel, because a byte of asynchronous data requires 10 bits-including stop and start bits-for transmission, but a byte of synchronous data requires only 8 bits. A 115.2Kbps DTE rate cannot properly support two 64Kbps B channels because the terminal adapter is unable to buffer the excess data when the incoming data for an ISDN line is 128Kbps.

 Figure 14-1 shows an example of an ISDN or switched 56Kbps connection.

  Example of an ISDN or Switched 56Kbps Connection

Configuration Steps for a Synchronous V.25bis Connection

To install your PortMaster, follow the instructions in your hardware installation guide. If you need additional help, refer to the troubleshooting chapter of the installation guide. The example in this chapter shows variables in italics. Change these values to reflect your network.

Once you have assigned an IP address to the PortMaster, continue with the following steps:

1. Configure the following settings for the PortMaster in Boston

a. Global settings (page 14-4)

b. Ethernet interface settings (page 14-4)

c. Synchronous port settings (page 14-5)

d. Dial-in users (page 14-6)

e. Dial-out locations (page 14-7)

1. Configure the following settings for the PortMaster in Miami:

a. Global settings (page 14-8)

b. Ethernet interface settings (page 14-9)

c. Synchronous port settings (page 14-9)

d. Dial-in users (page 14-10)

e. Dial-out locations (page 14-11)

1. Test the configuration (page 14-12).

2. Troubleshoot the configuration (page 14-13).

Configuring the PortMaster in Boston

Configuring Global Settings

Once you have configured the global settings shown in Table 14-1, save the configuration by using the following command:  

Command> save all

For more information about global settings, refer to Chapter 3, "Configuring Global Settings."

Configuring Ethernet Interface Settings

Once you have configured the Ethernet interface as shown in Table 14-2, save the configuration using the following command:  

Command> save all

For more information on Ethernet settings, refer to Chapter 4, "Configuring the Ethernet Interface."

Configuring Synchronous WAN Port Settings

Once you have configured the synchronous WAN port as shown in Table 14-3, reset the port and save the configuration using the following commands:  

Command> reset w1 Command> save all

For more information about synchronous ports, refer to Chapter 6, "Configuring a Synchronous WAN Port."

Configuring a Dial-In User

Once you have configured user table settings as shown in Table 14-4, save the configuration using the following command:  

Command> save all

No compression is used on synchronous lines. For more information about configuring user table settings, refer to Chapter 7, "Configuring Dial-In Users."

Configuring a Dial-Out Location

Note ¯ Configuring the maximum ports setting to a value higher than 0 causes the PortMaster to dial out to a continuous location, or become available for dial-out to an on-demand location. By configuring the maximum ports setting last, you ensure that the PortMaster will not attempt to make a connection with a location until you have configured all the settings for that location.

Once you have configured location table settings as shown in Table 14-5, save the configuration using the following command:  

Command> save all

For more information about configuring location table settings, refer to Chapter 8, "Configuring Dial-Out Connections."

Configuring the PortMaster in Miami

Configuring Global Settings

Once you have configured the global settings shown in Table 14-6, save the configuration by using the following command:  

Command> save all

For more information about global settings, refer to Chapter 3, "Configuring Global Settings."

Configuring Ethernet Interface Settings

Once you have configured the Ethernet interface as shown in Table 14-7, save the configuration using the following commands:  

Command> save all

For more information on Ethernet settings, refer to Chapter 4, "Configuring the Ethernet Interface."

Configuring Synchronous WAN Port Settings

Once you have configured the synchronous WAN port as shown in Table 14-8, reset the port and save the configuration using the following commands:  

Command> reset w1 Command> save all

For more information about synchronous ports, refer to Chapter 6, "Configuring a Synchronous WAN Port."

Configuring a Dial-In User

No compression is used on synchronous lines. Once you have configured user table settings as shown in Table 14-9, save the configuration using the following command:  

Command> save all

For more information about configuring user table parameters, refer to Chapter 7, "Configuring Dial-In Users."

Configuring a Dial-Out Location

Testing the Configuration

1. Enter the following commands to connect from the office in Miami to location boston:

   Command> set console w1 Command> set debug 0x51 Command> dial boston

2. Monitor the dial-and-connect sequence between the two locations.

3. If everything connects as expected, do the following:

a. Turn off debugging on the console:

Command> set debug isdn off Command> reset console

b. Reset the port on the Office Router in Miami and change the location type of location boston to on-demand:

Command> reset w1 Command> set location boston on_demand

1. If you notice a problem, do the following:

a. Reset the port.

b. Check your configuration.

c. Dial Boston again.

d. Repeat this procedure until the connection is made correctly.

1. When you have configured the PortMaster correctly, reset the port and save the configuration:

   Command> reset w1 Command> save all

Troubleshooting a Synchronous V.25bis Connection

If you are having trouble with a V.25bis dial-up connection to location Locname, verify the following:

• The error counters should be 0 except for a small number of abnormal termination errors resulting from plugging cables in or out. If your error counters are nonzero, the problem is external to the PortMaster.

• Verify that you are using the correct cables and that they are attached securely to the correct port. Not all WAN ports are capable of the same speeds.

• Verify that the DIP switch is set to V.35 for Livingston cables and that you are plugged into the correct V.35 interface on your CSU/DSU.

• Verify that the CSU/DSU or synchronous terminal adapter is providing the clock to the PortMaster. The CSU/DSU or terminal adapter can generate the clock or receive it from the carrier.

• Verify that the CSU/DSU or synchronous terminal adapter is configured properly.

• Use the following commands to view the PPP negotiation:

  Command> set console w1 Command> set debug 0x51 Command> dial Locname

For more information about the interpreting the results of the debug command, refer to "Debugging and Interpreting PPP Negotiation" on page 20-9. Once you have verified that the PPP negotiation is correct, use the following commands to turn off the debug utility:

Command> set debug off Command> reset console

• Contact your carrier to review your configuration and the status of their line.