Configuring modem dial backup

Last Updated : Jan 04, 2017 |

Procedure

  1. From the general context, use the show interfaces USB-modem command to verify that the modem is connected. You may be required to enable the modem.
  2. Enter interface dialer, followed by the identifier, to create the Dialer interface.

    For example:

    Gxxx-001(super)# interface dialer 1
Gxxx-001(if:dialer 1)#

    The Dialer interface is created and can now be defined as a backup interface for an existing WAN interface.

  3. Enter up to five dialer strings, using the dialer string command.

    For example:

    Gxxx-001(if:dialer 1)# dialer string 1 5555555
Done!
Gxxx-001(if:dialer 1)# dialer string 2 1234567
Done!

    When the Dialer interface is activated, the Dialer first attempts to dial the number associated with dialer string 1. If that attempt fails, the Dialer attempts to connect to the number associated with the next dialer string, and so on.

  4. Set the IP address of the Dialer interface with the ip address command.

    There are three options:

    • Manually set the IP address and subnet mask. Use this option when you know to which server the dialed string is going to connect. For example:

      Gxxx-001(if:dialer 1)# ip address 4.5.6.7 255.255.255.0
Done!

    • Enter ip address negotiated.

    • Enter ip unnumbered interface, where interface is the name of another interface in the gateway (for example, the WAN interface) from which an IP address for the Dialer interface is borrowed. Use this command when you do not know who will eventually be your peer and you want to run dynamic routing protocols (for example, OSPF or RIP) over the dialup link.

  5. Enter dialer persistent initial delay, with the value 30 seconds, to prevent dialup after boot, before the WAN link is fully functional.

    For example:

    Gxxx-001(if:dialer 1)# dialer persistant initial delay 30
Done!
  6. If needed, set any of the following parameters:

    • Use the dialer persistent max-attempts command to set the maximum number of dial attempts. For example:

      Gxxx-001(if:dialer 1)# dialer persistent max-attempts 10
Done!

      The Dialer interface dials each number associated with a dialer string, in order, until either a connection is made, or the number configured in the dialer persistent max-attempts command is reached.

    • Use the dialer persistent re-enable command to enable and configure a timer to re-enable dial attempts after the maximum number of dial attempts has been reached. For example:

      Gxxx-001(if:dialer 1)# dialer persistent re-enable 3600
Done!

    • Use the dialer order command to set which dial strings are used upon a new dial trigger event. The default is to restart from the beginning of the dial list. For example:

      Gxxx-001(if:dialer 1)# dialer order last-successful
Done!

    • Use the dialer persistent command to force the dialer to attempt to reconnect every second, or at another redial interval, which you can configure using the dialer persistent delay command. By default, redialing is disabled. For example:

      Gxxx-001(if:dialer 1)# dialer persistent
Done!
Gxxx-001(if:dialer 1)# dialer persistent delay 10
Done!

    • Use the dialer wait-for-ipcp command to set the maximum time the dialer waits between dialing a number to successfully establishing PPP/IPCP. The default is 45 seconds. For example:

      Gxxx-001(if:dialer 1)# dialer wait-for-ipcp 100
Done!
  7. Configure an authentication method and parameters, if required:

    • For PAP authenticating, enter ppp pap sent-username followed by a username and password. For example:

      Gxxx-001(if:dialer 1)# ppp pap sent-username avaya32 password ******
Done!

    • For CHAP authentication, enter ppp chap hostname followed by a hostname, and ppp chap password followed by a password. For example:

      Gxxx-001(if:dialer 1)# ppp chap hostname avaya32
Done!
Gxxx-001(if:dialer 1)# ppp chap password 123456
Done!
  8. From the general context, use show interfaces dialer 1 to verify that the Dialer interface has connected to the remote peer.

    For example:

    Gxxx-001(super)# show interfaces dialer 1
Dialer 1 is down, line protocol is down
 Internet address is 4.5.6.7, mask is 255.255.255.0
 MTU 1500 bytes, Bandwidth 28 kbit
 IPSec PMTU: copy df-bit, Min PMTU is 300
 Reliability 1/255 txLoad 255/255 rxLoad 255/255
 Encapsulation PPP
 Link status trap disabled
 Keepalive track not set
 Keepalive set (10 sec)
 LCP  Starting
 IPCP Starting
 Last dialed string:
 Dial strings:
    1: 5555555
    2: 1234567
 Dialing order is sequential
 Persistent initial delay 5 sec
 Wait 45 sec for IPCP
 Weighted Fair VoIP queueing mode
 Last input never, Last output never
 Last clearing of 'show interface' counters never
 5 minute input rate 0 bits/sec, 0 packets/sec

    This command shows the interface status, including a summary of its definitions and settings. The status also tells you whether the interface is up and the dialup succeeded. In the example status, the interface is down and inactive.

  9. Enter the context of the interface which the Dialer is to back up, and use the backup interface command to configure the Dialer interface as the backup interface.

    For example:

    G430-001(if:Tunnel 1)# backup interface dialer 1
Done!

    Interface Dialer 1 is now selected as the backup interface to the selected interface. The Dialer interface is activated in the event of a failure of the primary interface. Upon activation, the Dialer interface dials the number associated with the first dialer string.

  10. From the general context, use the ip default-gateway dialer command to configure backup routing.

    The following example configures a simple low priority via static route:

    Gxxx-001(super)# ip default-gateway dialer 1 1 low
Done!
    Note:

    Define multiple routes to ensure that traffic reaches the Dialer interface.