| You can control whether
addressing is dynamic (the user specifies the address at the EXEC
level when making the connection), or whether default addressing is
used (the address is forced by the system). If you specify dynamic
addressing, the router must be in interactive mode and the user
enters the address at the EXEC level.
It is common to configure an
asynchronous interface to have a default address and to allow
dynamic addressing. With this configuration, the choice between the
default address or dynamic addressing is made by the users when they
enter the ppp EXEC level command. If the user
enters an address, it is used; if the user enters the default
keyword, the default address is used.
You can, therefore, configure the
router to do one of the following:
- Assign a default async address
or
- Allow an async address to be
assigned dynamically by the caller
Assigning a Default Async
Address
To assign a predefined default IP
address to the remote client node that dials in to the
corresponding asynchronous line, use the
peer default ip address
command as shown in the Figure. Additionally, the pool and dhcp
arguments allow address allocation from a local pool of addresses
or a Dynamic Host Configuration Protocol (DHCP) server. The
peer default ip address
command first appeared in IOS
11.0. Before 11.0, the
async interface
command was used instead (for
example,
async default ip address address).
Router(config-if)#peer
default ip address{ip-address | dhcp | pool
poolname}
Additionally, the pool and dhcp
options to the peer default ip address command require a
global command to create the pool of addresses; for example, ip
local pool pool-name starting-address end-address.
DHCP Consideration
If the peer default ip dhcp
option is chosen, you have to also configure ip helper address
and ip dhcp-server.
Allowing an Async Address to Be
Assigned Dynamically
The async dynamic address
allows the remote dial-in client to enter its own IP address, if it
has one:
Router(config-if)#async
dynamic address
When a line is configured for dynamic
assignment of asynchronous addresses, the user enters the slip
or ppp EXEC command, and is prompted for an address or
logical host name. Assigning asynchronous addresses dynamically is
also useful when you want to assign set addresses to users. For
example, an application on a personal computer that automatically
dials in using SLIP and polls for electronic mail messages can be
set up to dial in periodically, and then enter the required IP
address and password.
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