Specifications

Configuring Asynchronous Lines and Interfaces
How to Configure Other Asynchronous Line and Interface Features
DC-31
Cisco IOS Dial Technologies Configuration Guide
In interactive mode, a line can be used to make any type of connection, depending on the EXEC
command entered by the user. For example, depending on its configuration, the line could be used for
Telnet or XRemote connections, or SLIP or PPP encapsulation. The user is prompted for an EXEC
command before a connection is initiated.
You can configure an asynchronous interface to be in dedicated network mode. When the interface is
configured for dedicated mode, the end user cannot change the encapsulation method, address, or other
parameters.
To configure an interface for dedicated network mode or to return it to interactive mode, use one of the
following commands in interface configuration mode:
By default, no asynchronous mode is configured. In this state, the line is not available for inbound
networking because the SLIP and PPP connections are disabled.
See the “Dedicated Asynchronous Interface Configuration Example” section for an example of how to
configure a dedicated asynchronous interface.
Conserving Network Addresses
When asynchronous routing is enabled, you might need to conserve network addresses by configuring
the asynchronous interfaces as unnumbered. An unnumbered interface does not have an address.
Network resources are therefore conserved because fewer network numbers are used and routing tables
are smaller.
To configure an unnumbered interface, use the following command in interface configuration mode:
Whenever the unnumbered interface generates a packet (for example, a routing update), it uses the
address of the specified interface as the source address of the IP packet. It also uses the address of the
specified interface to determine which routing processes are sending updates over the unnumbered
interface.
You can use the IP unnumbered feature even if the system on the other end of the asynchronous link does
not support it. The IP unnumbered feature is transparent to the other end of the link because each system
bases its routing activities on information in the routing updates it receives and on its own interface
address.
See the “Network Address Conservation Using the ip unnumbered Command Example” section for an
example of how to conserve network addresses.
Command Purpose
Router(config-if)# async mode dedicated
Places the line into dedicated asynchronous network mode.
Router(config-if)# async mode interactive
Returns the line to interactive mode.
Command Purpose
Router(config-if)# ip unnumbered type number
Conserves IP addresses by configuring the asynchronous
interfaces as unnumbered, and assigns the IP address of the
interface type that you want to leverage.