Cisco Networking Academy Program

1
Cisco Networking Academy Program

• Semester 4
• Module 2
• Async Communication

2
Connecting a Modem To a Router

• AUX (Auxiliary) To connect a modem to a Cisco
  router's AUX port, you typically use a rollover
  cable and a RJ-45-to-DB-25 male DCE modem adapter
  
• Console Modems are rarely connected to them.
  This is because the console port does not support
  hardware flow control. The Request to Send (RTS)
  and Clear to Send (CTS) pins are not supported

3
Connecting a Modem To a Router

• Connecting to a serial interface
• physical-layer async interface command
• The Picture shows a connection between a Cisco
  2620 series router and an external modem using an
  EIA/TIA-232 Smart Serial cable.

4
Connecting a Modem To a Router

• Connecting a modem to an Access Server Async
  Lines
• Cisco Systems applies the term "access server"
  only to devices built especially as concentration
  points for dial-in and dial-out calls.

68 Pin Async Port
5
Connecting a Modem to a PC

• You can Connect an external modem using a
  rollover cable and and RJ-45-to-DB-25 male DCE
  adapter, which is attached to the modem. One end
  of the rollover cable connects to the DB-25
  adapter on the modem. The other end of the
  rollover cable connects to a 9-pin serial port on
  the PC (also called a COM port).

6
Connecting to the Modem-Reverse Telnet

• Some modems can be configured by using a panel on
  the unit however, most modems don't have
  configuration panels.
• Instead, you must access the modem's software via
  another device such as an access server. When
  using a Cisco access server, you have the option
  to manually configure the modem or automatically
  configure the modem using a script.
• Manual configurations are accomplished using a
  technique called reverse Telnet.

7
Connecting to the Modem-Reverse Telnet
8
Connecting to the Modem-Reverse Telnet

• When using reverse Telnet, you can use the telnet
  command to connect to any IP address configured
  on the router, as long as the interface
  associated with that IP address is up.
• Typically, you configure the access server with a
  loopback IP address. Since a loopback interface
  is a logical interface, it is not susceptible to
  physical failures.

9
Lines Type and Numbering

• Different router models number the line types in
  different ways. The figure shows the Cisco
  line-numbering rules, where n represents the
  first physical line after the console line, and m
  refers to the number of the vty line
• For example, the VTY 4 line corresponds to line
  14 on a router with eight TTY ports. Because line
  0 is for the console, lines 1 to 8 are the TTY
  lines, line 9 is for the auxiliary port, and
  lines 10 to 14 are for VTY 0 to 4.

10
Lines Type and Numbering

• Reverse Telnet connections to an individual line
  can be used to communicate and configure an
  attached device.
• To connect to an individual line, the remote host
  or terminal must specify a particular TCP port on
  the access server.
• For reverse Telnet, that port is 2000 plus the
  line number. For example telnet 131.108.30.40
  2001
• This command indicates a Reveres Telnet
  connection to line 1 (2000 1).
• If you want to reverse Telnet to a modem on line
  14, you would use TCP port 2014.

11
Lines Type and Numbering
12
Configuring Reverse Telnet

• RTAconfigure terminalRTA(config)line
  10RTA(config-line)transport input
  allRTA(config-line)modem inout
• Transport input all allows all of the following
  protocols to be used for the connection LAT,
  MOP, NASI, PAD, rlogin, Telnet, and v120. Each of
  these protocols can be specified individually as
  a command option
• The modem inout command is required to permit
  both incoming and outgoing connections on a given
  line.

13
Configuring Reverse Telnet
14
Basic Terminal Line Configuration
Most AUX ports are limited to 38400 bps, although
AUX ports on 2600 and 3600 series routers support
speeds up to 115200 bps.