Remote Access Exam Cram
6.0 Line Numbers - Cisco devices have the line numbers assigned in the following manner:
Console line (CON): Assigned line number 0
Asynchronous lines (TTY): Assigned line number n, where n represents the first physical line after the Console line. For example, TTY line 4 is assigned line number 4.
Auxiliary line (AUX): The auxiliary line is assigned the last TTY (async) line + 1. For example, if there can be n TTY lines, the Auxiliary line is assigned n+1. Note that the TTY lines are as recognized by Cisco IOS and not necessarily be present physically.
6.1 The Interface number of a port in a Cisco 3600 router is calculated as below:
Interface number = 32Xslot number + Unit number + 1
Note that slot numbers and port numbers start at 0.
For 3640, there are 4 network module slots, ranging from 0 to 3. The line number for slot 1, port 9 is given as below:
32X1 + 9 + 1 = 42.
Also, note that the interface number is same for a given slot/port combination irrespective of whether the other modules are of different type (like 8 port or 16 port or 32 port) or even empty.
Note that line 0 is always used by console port. The async lines start from line 1 onwards. For 3620, there are two network module slots. Therefore, the line numbers are assigned as below by IOS software:
Console: Line 0
Slot 0 (Port #s 0 to 31): Line 1 to 32
Slot 1 (Port #s 0 to 31): Line 33 to 64
Aux. Port: Line 65. Note that Auxiliary port is assigned a line number next to async lines (async lines are also known as tty lines).
7.0 Asynchronous Communications:
There are two different kinds of configurations required to make an asynchronous port to place and receive calls. These are:
1. Line configuration
2. Interface configuration.
Line configuration commands allow you to configure the modem parameters such as line speed, flow control, etc.
Interface configuration commands allow you to configure the protocol aspects such as encapsulation, authentication etc. The distinction between these two configurations must be known clearly!
7.1 Given below are various types of interfaces / cables that are supported for connecting Cisco routers to the
1. Asynchronous connections make use of RJ-11 cables between the modem's line port ad the telephone company jack. If the modem is external to the router, a EIA/TIA-232 cable is required between the router and the modem. DB-60 end of the cable is connected to the router and DB-25 end of the cable is connected to the modem.
2. ISDN BRI connections make use of RJ-45 cables between the BRI interface and the ISDN network.
3. ISDN PRI connections in North America are done in either of two ways:
3.1. Internal CSU: Routers with internal CSU modules attach directly to the ISDN network with a standard JR-48 connector.
3.2. External CSU: DB-15 female end of the cable is attached to the router, and the other end is attached to the CSU. The CSU in turn is attached to the ISDN network.
4. For Frame Relay connection, the following signaling standards are supported by Cisco routers:
EIA/TIA-232, EIA/TIA-449, V.35, X.21 and EIA-530. The router end of the serial cable is always a DB-60 port sitting on the serial interface of the router.
8. Chat Scripts - Chat-scripts are divided into two types:
1. Modem scripts: These are sent between the DTE and DCE.
2. System scripts: These are sent between the DTE and DTE.
The chat-script consists of simple "Expect - Send" pairs. The local device 'expects' certain word, and sends a matching word.
Chat-scripts can be used to do the following:
1. Initializing the directly attached modem,
2. Instructing the modem to dial out or logging in to a remote system,
3. Detection of errors etc.
9. Access Servers:
Async interfaces on Access Servers can be configured in one of two modes:
1. Dedicated - In this mode, an interface is automatically configured for SLIP or PPP. The end user cannot change the encapsulation method, address, etc. basically there will be no user prompt or EXEC level.
The command used for this is:
Router(config-if)# async mode dedicated
2. Interactive - In this mode, the user prompt or EXEC level are available to the dial-in user. Therefore, the dial-in user can select whether to run SLIP, PPP, or Telnet etc. interactively.
The command 'autoselect' is used to autosense between arap, ppp, or slip. This command needs to be given only after the command async mode interactive is given. If you try to give 'autoselect' command without first issuing 'async mode interactive', you will get an error message.
Finally, the command
Router(config-if)# async dynamic address - is used to allow the remote dial-in client to enter its own IP address.
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