System information

Troubleshooting Dialin Connections 16-365
Dialin: Modem Cannot Send or Receive IP Data
Hardware flow control not
configured on local or remote
modem or router
Step 2 Configure hardware flow control on the line using the flowcontrol
hardware line configuration command.
To set the method of data flow control between the terminal or other
serial device and the router, use the flowcontrol line configuration
command. Use the no form of this command to disable flow control.
Syntax:
flowcontrol {none | software [lock][in | out]|hardware [in | out]}
Syntax Description:
• none—Turns off flow control.
• software—Sets software flow control. An optional keyword
specifies the direction: in causes the Cisco IOS software to listen
to flow control from the attached device, and out causes the
software to send flow control information to the attached device. If
you do not specify a direction, both are assumed.
• lock—Makes it impossible to turn off flow control from the
remote host when the connected device needs software flow
control. This option applies to connections using the Telnet or
rlogin protocols.
• hardware—Sets hardware flow control. An optional keyword
specifies the direction: in causes the software to listen to flow
control from the attached device, and out causes the software to
send flow control information to the attached device. If you do not
specify a direction, both are assumed. For more information about
hardware flow control, see the hardware manual that was shipped
with your router.
Example:
The following example sets hardware flow control on line 7:
line 7
flowcontrol hardware
Note: If for some reason you cannot use flow control, limit the line
speed to 9600 bps. Faster speeds are likely to result in lost data.
Hardware flow control not
configured on local or remote
modem or router
Step 3 After enabling hardware flow control on the access server or router
line, initiate a reverse Telnet session to the modem via that line. For
more information, see the section “Establishing a Reverse Telnet
Session to a Modem.”
Step 4 Use a modem command string that includes the RTS/CTS Flow
command for your modem. This command ensures that the modem
is using the same method of flow control (that is, hardware flow
control) as the Cisco access server or router. See your modem
documentation for exact configuration command syntax. Figure 16-1
shows the hardware flow control command string for a
Hayes-compatible modem.
Possible Causes Suggested Actions