Configuring Dial Backup and Remote Management
The Cisco 1800 integrated services fixed-configuration routers support dial-in (for remote management) and dial-out (for dial backup) capabilities. By allowing you to configure a backup modem line connection, the Cisco 1800 integrated services fixed-configuration routers provide protection against WAN downtime. Dial backup is inactive by default, and must be configured to be active.
Dial backup and remote management functions are configured through the ISDN S/T port of the Cisco 1812, Cisco 1801, Cisco 1802, and Cisco 1803 routers. These functions are configured through the V.92 modem port of the Cisco 1811 router.
This chapter contains the following topics:
Dial Backup Feature Activation Methods
Three methods are available to activate the dial backup feature:
Backup Interfaces
When the router receives an indication that the primary line is down, a backup interface is brought up. You can configure the backup interface to go down once the primary connection has been restored for a specified period.
This is accomplished using dial-on-demand routing (DDR). When this is configured, a backup call is triggered by specified traffic.
Note Even if the backup interface comes out of standby mode (is brought up), the router does not trigger the backup call unless it receives the specified traffic for that backup interface.
Configuring Backup Interfaces
Perform these steps to configure your router with a backup interface, beginning in global configuration mode:
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Step 1
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interface type number
Example:
Router(config)#
interface atm 0
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Enters interface configuration mode for the interface for which you want to configure backup.
This can be a serial interface, ISDN interface, or asynchronous interface.
The example shows the configuration of a backup interface for an ATM WAN connection.
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Step 2
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backup interface interface-type interface-number
Example:
Router(config-if)#
backup
interface bri 0
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Assigns an interface as the secondary, or backup interface.
This can be a serial interface or asynchronous interface. For example, a serial 1 interface could be configured to back up a serial 0 interface.
The example shows a Basic Rate Interface configured as the backup interface for the ATM 0 interface.
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Step 3
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exit
Example:
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Enters global configuration mode.
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Floating Static Routes
Floating static routes provide alternative routes for traffic. Floating static routes are not activated unless a DDR backup call has been triggered by specified traffic for a backup interface.
Floating static routes are independent of line protocol status. This is an important consideration for Frame Relay circuits because the line protocol may not go down if the data-link connection identifier (DLCI) is inactive. Floating static routes are also encapsulation independent.
Note When static routes are configured, the primary interface protocol must go down in order to activate the floating static route.
Configuring Floating Static Routes
Static and dynamic routes are the two components of floating static routes. Perform these steps to configure the static and dynamic routes on your router, beginning in global configuration mode:
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Step 1
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ip route
prefix mask
{
ip-address
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interface-type
interface-number
[
ip-address
]}
Example:
Router(config)# ip route 0.0.0.0 0.0.0.0 22.0.0.2
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Assigns the primary static route.
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Step 2
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ip route
prefix mask
{
ip-address
|
interface-type
interface-number
[
ip-address
]} [
distance
]
Example:
Router(config)# ip route 0.0.0.0 0.0.0.0 192.168.2.2 150
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Assigns the lower routing administrative distance value for the backup interface route. 192.168.2.2 is the peer IP address of the backup interface.
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Step 3
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router rip
Example:
Router(config)#
router ri
p
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Enables RIP routing.
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Step 4
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network
ip-address
Example:
Router(config)#
network 22.0.0.0
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Defines the primary interface network. 22.0.0.0 is the network value of the primary interface.
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Step 5
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ip route
prefix mask
{
ip-address
|
interface-type
interface-number
[
ip-address
]} [
distance
]
Example:
Router(config)# ip route 0.0.0.0 0.0.0.0 192.168.2.2 150
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Assigns the lower routing administrative distance value for the backup interface route. 192.168.2.2 is the peer IP address of the backup interface.
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Note When dynamic routing is activated, the floating static route depends upon routing protocol convergence times.
Dialer Watch
The dialer watch method only supports the Extended Interior Gateway Routing Protocol (EIGRP) link-state dynamic routing protocols.
Configuring Dialer Watch
Perform these steps to configure a dialer watch on your router, beginning in global configuration mode:
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Step 1
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interface type number
Example:
Router(config)#
interface dialer 2
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Enters configuration mode for the dial backup interface.
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Step 2
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dialerwatch-group group-number
Example:
Router(config-if)#
dialer watch-group 2
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Specifies the group number for the watch list.
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Step 3
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exit
Example:
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Enters global configuration mode.
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Step 4
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ip route
prefix mask
{
ip-address
|
interface-type
interface-number
[
ip-address
]} [
distance
]
Example:
Router(config)# ip route 0.0.0.0 0.0.0.0 22.0.0.2
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Assigns the primary route. 22.0.0.2 is the peer IP address of the primary interface.
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Step 5
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ip route
prefix mask
{
ip-address
|
interface-type
interface-number
[
ip-address
]} [
distance
]
Example:
Router(config)# ip route 0.0.0.0 0.0.0.0 192.168.2.2 150
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Assigns the lower routing administrative distance value for the backup interface route. 192.168.2.2 is the peer IP address of the backup interface.
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Step 6
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dialerwatch-list group-number
{
ip
ip-address address-mask
|
delay route-check initial
seconds
}
Example:
Router(config)#
dialer watch-list 2 ip 22.0.0.2 255.255.255.255
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Assigns an IP address to the watch list.
If the connection on the primary interface is lost and the IP address is unavailable on the router, the dial-out feature on the backup interface is triggered. 22.0.0.2 is the peer IP address of the primary interface.
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Dial Backup Feature Limitations
The following limitation exists for the dial backup feature: bridging is not supported over console or auxiliary port backup interfaces.
Table 13-1
summarizes dial backup support and limitations for the Cisco 1800 series integrated services fixed-configuration routers.
Table 13-1 Dial Backup Feature Support and Limitations Summary
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PPPoE
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Yes
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Dialer watch
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Bridging is not supported across a slow interface, for example, an auxiliary port. The peer IP address of the ISP is needed to configure the dialerwatch command and the IP static route.
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Normal IP in cable modem scenario
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No
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Dialer watch
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The IP addresses of the peers are needed for dialer watch to work properly. If a lease time obtained by DHCP is not set short enough (1 or 2 minutes), dial backup is not supported.
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Cisco 1801, Cisco 1802, or Cisco 1803
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PPP over ATM
PPP over Ethernet
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Yes
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Backup interfaces
Floating static routes
Dialer watch
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Floating static route and dialer watch need a routing protocol to run in the router. The dialer watch method brings up the backup interface as soon as the primary link goes down. The backup interface is brought down as soon as the dialer timeout is reached and the primary interface is up. The router checks the primary interface only when the dialer timeout expires. The backup interface remains up until the dialer timeout is reached, even though the primary interface is up.
For the dialer watch method, a routing protocol does not need to be running in the router, if the IP address of the peer is known.
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RFC 1483 (AAL5, SNAP, and MUX)
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Yes
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Backup interfaces
Floating static routes
Dialer watch
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If bridging is done through the WAN interface, it is not supported across the auxiliary port.
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Configuration Example
The following three examples show sample configurations for the three dial backup methods.
Example 13-1 Configuring Dial Backup Using Backup Interfaces
!Specifies the ISDN switch type isdn switch-type basic-net3 ip address 192.168.1.1 255.255.255.0 !ISDN interface to be used as a backup interface isdn switch-type basic-net3 pppoe-client dial-pool-number 2 ! Dial backup interface, associated with physical BRI0 interface. Dialer pool 1 associates it with BRI0’s dialer pool member 1 ! Primary interface associated with physical ATM0’s interface, dialer pool 2 associates it with ATM0’s dial-pool-number2 !Primary and backup interface given route metric ip route 0.0.0.0 0.0.0.0 22.0.0.2 ip route 0.0.0.0 0.0.0.0 192.168.2.2 80 !Specifies interesting traffic to trigger backup ISDN traffic dialer-list 1 protocol ip permit
Example 13-2 Configuring Dial Backup Using Floating Static Routes
!Specifies the ISDN switch type isdn switch-type basic-net3 ip address 192.168.1.1 255.255.255.0 !ISDN interface to be used as a backup interface isdn switch-type basic-net3 pppoe-client dial-pool-number 2 ! Dial backup interface, associated with physical BRI0 interface. Dialer pool 1 associates it with BRI0’s dialer pool member 1 ! Primary interface associated with physical ATM0’s interface, dialer pool 2 associates it with ATM0’s dial-pool-number2 !Primary and backup interface given route metric (This example using static routes, thus atm0 line protocol must be brought down for backup interface to function.) ip route 0.0.0.0 0.0.0.0 22.0.0.2 ip route 0.0.0.0 0.0.0.0 192.168.2.2 150 !Specifies interesting traffic to trigger backup ISDN traffic dialer-list 1 protocol ip permit
Example 13-3 Configuring Dial Backup Using Dialer Watch
!Specifies the ISDN switch type isdn switch-type basic-net3 ip address 192.168.1.1 255.255.255.0 !ISDN interface to be used as a backup interface isdn switch-type basic-net3 pppoe-client dial-pool-number 2 ! Dial backup interface, associated with physical BRI0 interface. Dialer pool 1 associates it with BRI0’s dialer pool member 1. Note “dialer watch-group 1” associates a watch list with corresponding “dialer watch-list” command ! Primary interface associated with physical ATM0 interface, dialer pool 2 associates it with ATM0’s dial-pool-number2 !Primary and backup interface given route metric ip route 0.0.0.0 0.0.0.0 22.0.0.2 ip route 0.0.0.0 0.0.0.0 192.168.2.2 80 !Watch for interesting traffic dialer watch-list 1 ip 22.0.0.2 255.255.255.255 !Specifies interesting traffic to trigger backup ISDN traffic dialer-list 1 protocol ip permit
Configuring Dial Backup and Remote Management Through the ISDN S/T Port
The Cisco 1812, Cisco 1801, Cisco 1802, and Cisco 1803 routers use the ISDN S/T port for dial backup and remote management. Perform the following tasks to configure dial backup and remote management through the ISDN S/T port of your router:
• Configure ISDN Settings
Configure ISDN Settings
Note Traffic of interest must be present to activate the backup ISDN line by means of the backup interface and floating static routes methods. Traffic of interest is not needed for the dialer watch to activate the backup ISDN line.
Perform these steps to configure your router ISDN interface for use as a backup interface, beginning in global configuration mode:
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Step 1
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isdn switch-type switch-type
Example:
Router(config)#
isdn switch-type basic-net3
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Specifies the ISDN switch type.
The example specifies a switch type used in Australia, Europe, and the United Kingdom. For details on other switch types supported, see the
Cisco IOS Dial Technologies Command Reference
.
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Step 2
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interface type number
Example:
Router(config)#
interface bri 0
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Enters configuration mode for the ISDN Basic Rate Interface (BRI).
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Step 3
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encapsulation encapsulation-type
Example:
Router(config-if)#
encapsulation ppp
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Sets the BRI0 interface encapsulation type.
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Step 4
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dialer pool-member number
Example:
Router(config-if)#
dialer pool-member 1
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Specifies the dialer pool membership.
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Step 5
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isdn switch-type switch-type
Example:
Router(config-if)#
isdn switch-type basic-net3
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Specifies the ISDN switch type.
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Step 6
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exit
Example:
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Enters global configuration mode.
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Step 7
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interface dialer dialer-rotary-group-number
Example:
Router(config)#
interface dialer 0
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Creates a dialer interface (numbered 0–255) and enters into interface configuration mode.
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Step 8
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ip address negotiated
Example:
Router(config-if)#
ip address negotiated
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Specifies that the IP address for the interface is obtained through PPP/IPCP (IP Control Protocol) address negotiation. The IP address is obtained from the peer.
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Step 9
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encapsulation encapsulation-type
Example:
Router(config-if)#
encapsulation ppp
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Sets the encapsulation type to PPP for the interface.
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Step 10
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dialer pool number
Example:
Router(config-if)#
dialer pool 1
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Specifies the dialer pool to be used.
In the example, the dialer pool 1 setting associates the dialer 0 interface with the BRI0 interface because the BRI0 dialer pool-member value is 1.
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Step 11
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dialer string dial-string
[
:
isdn-subaddress
]
Example:
Router(config-if)#
dialer string 384040
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Specifies the telephone number to be dialed.
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Step 12
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dialer-group group-number
Example:
Router(config-if)#
dialer group 1
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Assigns the dialer interface to a dialer group (1–10).
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Step 13
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exit
Example:
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Exits the dialer 0 interface configuration mode, and enters global configuration mode.
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Step 14
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dialer-list
dialer-group
protocol
protocol-name
{
permit
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deny
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list
access-list-number
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access-group
}
Example:
Router(config)# dialer-list 1 protocol ip permit
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Creates a dialer list for packets of interest to be forwarded through the specified interface dialer group.
In the example, dialer-list 1 corresponds to dialer-group 1.
For details about this command and additional parameters that can be set, see the
Cisco IOS Dial Technologies Command Reference
.
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Configure the Aggregator and ISDN Peer Router
The aggregator is typically a concentrator router where your Cisco router ATM PVC terminates. In the configuration example shown below, the aggregator is configured as a PPPoE server to correspond with the Cisco 876 router configuration example that is given in this chapter.
The ISDN peer router is any router that has an ISDN interface and can communicate through a public ISDN network to reach your Cisco router ISDN interface. The ISDN peer router provides Internet access for your Cisco router during the ATM network downtime.
!This portion of the example configures the aggregator ip address 40.1.1.1 255.255.255.0 ip address 30.1.1.1 255.255.255.0 interface Virtual-Template1 ip address 22.0.0.2 255.255.255.0 peer default ip address pool adsl ip local pool adsl 22.0.0.1 ip route 0.0.0.0 0.0.0.0 22.0.0.1 50 ip route 0.0.0.0 0.0.0.0 30.1.1.2.80 !This portion of the example configures the ISDN peer isdn switch-type basic-net3 ip address 30.1.1.2 255.0.0.0 description “to 836-dialbackup” isdn switch-type basic-net3 ip address 192.168.2.2 255.255.255.0 peer default ip address pool isdn ip local pool isdn 192.168.2.1 ip route 0.0.0.0 0.0.0.0 192.168.2.1 ip route 40.0.0.0 255.0.0.0 30.1.1.1 dialer-list 1 protocol ip permit
Configuring Dial Backup and Remote Management Through a V.92 Modem
Perform the following tasks to configure dial backup and remote management through the V.92 modem on your Cisco 1811 router:
• Asynchronous Interface Configuration
Asynchronous Interface Configuration
Perform these steps to configure the V.92 modem for use as a backup interface, beginning in global configuration mode:
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Step 1
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interface
type
number
Example:
Router(config)#
interface async 1
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Enters interface configuration mode for the asynchronous serial interface. Enter the number of the interface you want to configure.
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Step 2
|
ip unnumbered
type
number
Example:
Router(config-if)#
ip unnumbered FastEthernet 2
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Conserves IP addresses by configuring the asynchronous interface as unnumbered, and assigns the IP address of the interface type that you want to leverage.
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Step 3
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encapsulation encapsulation-type
Example:
Router(config-if)#
encapsulation ppp
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Sets the encapsulation type to PPP for the interface.
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Step 4
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dialer in-band
Example:
Router(config-if)#
dialer in-band
|
Specifies support for dial-on-demand routing (DDR) and chat scripts on this asynchronous interface.
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Step 5
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dialer string dial-string
Example:
Router(config-if)#
dialer string T14085551234
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Specifies the telephone number to be dialed.
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Step 6
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dialer-group group-number
Example:
Router(config-if)#
dialer group 1
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Assigns the dialer interface to a dialer group (1–10), controlling access. The number to which the dialer access group belongs is defined with the
dialer-list
command.
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Step 7
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async mode interactive
Example:
Router(config-if)#
async mode interactive
Router(config-if)#
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Returns a line that has been placed into dedicated asynchronous network mode to interactive mode, thereby enabling the Serial Line Internet Protocol (SLIP) and PPP EXEC commands.
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Step 8
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peer default ip address
{
ip-address
|
pool
[
pool-name
]}
Example:
Router(config-if)#
peer default ip address pool pool123
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Assigns IP addresses to remote clients, using an address pool. To create an IP address pool, use the
ip local pool
global configuration command.
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Step 9
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exit
Example:
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Exits asynchronous interface configuration, and enters global configuration mode.
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Line Configuration
Perform these steps to configure the line on the V.92 modem, beginning in global configuration mode:
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Step 1
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line
line-number
Example:
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Identifies a specific line for configuration and enters line configuration collection mode.
Note The number entered here must be the same as the number entered for the asynchronous serial interface.
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Step 2
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modem inout
Example:
Router(config-line)#
modem inout
|
Configures the line for both incoming and outgoing calls.
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Step 3
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autoselect
{
arap
|
ppp
|
slip
|
during-login
|
timeout
seconds
}
Example:
Router(config-line)#
autoselect ppp
|
Configures the line to automatically start an AppleTalk Remote Access (ARA), PPP, or SLIP session.
for use with the dial backup feature.
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Step 4
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transport input
{
all
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lat
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mop
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nasi
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none
|
pad
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rlogin
|
telnet
|
v120
}
Example:
Router(config-line)#
transport input all
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Defines which protocols can be used to connect to the line.
for use with the dial backup feature.
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Step 5
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exit
Example:
Router(config-line)#
exit
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Exits line configuration mode, and enters global configuration mode.
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