3-4 Dial Backup | Cisco Field Manual[c] Router Configuration

Dial backup monitors a specific router interface to determine the need for a backup connection. If the interface is down or if a traffic threshold is exceeded, the backup interface is brought up.
Dialer Watch can be used to watch for the deletion of specific routes that correspond to a remote router interface or an advertised network. If no routes to the address are found, the backup interface is brought up, and a call is made.
Dialer Watch is useful when the state of a local router interface does not reflect a failed connection.

Dial Backup Configuration

Identify the interface to be backed up:
```
 (global)  interface   type slot/port  
```
Specify the backup interface:
```
 (interface)  backup interface   type slot/port  
```
The backup interface is a dialer interface that DDR uses to make a call.
(Optional) Set a traffic threshold to trigger the backup:
```
 (interface)  backup load  {  enable-threshold   never  }   {  disable-threshold   never  } 
```
Dial backup is triggered when the traffic load exceeds the enable-threshold percentage (1 to 100 percent) of the available link bandwidth. Dial backup is disabled when the traffic load falls under the disable-threshold percentage (1 to 100 percent) of the link bandwidth. The never keyword can be used to cause dial backup to never be enabled or never be disabled.

NOTE

If the traffic threshold is not defined, dial backup is triggered only if the primary interface goes down.
(Optional) Wait until the primary interface changes state:
```
 (interface)  backup delay  {  enable-delay-period   never  }   {  disable-delay-  x  period   never  } 
```
When the primary interface goes down, dial backup waits for enable-delay-period (the default is 0 seconds) before triggering the backup call. When the primary interface comes back up, dial backup waits for disable-delay-period (the default is 0 seconds) before disabling the backup call. The never keyword can be used to never enable or never disable dial backup based on the primary interface state.
Make sure DDR is configured to use the backup interface. Refer to Section 3-3 for more configuration details if needed.

Dial Backup Example

Dial backup is configured so that when interface serial 0 goes down, DDR uses interface dialer 1 to make a backup connection. Dialer 1 is a logical interface that looks to dialer pool 5 to find an available interface for a new call. Interface serial 0 identifies interface dialer 1 as the backup interface, with an enable delay of 10 seconds and a disable delay of 20 seconds. Once dial backup is triggered, DDR uses dialer list 1 to specify the "interesting" traffic to actually trigger the call. Here, the dialer list triggers by permitting any IP traffic:

  interface dialer 1   ip address 192.168.1.1 255.255.255.0   encapsulation ppp   dialer string 5551111   dialer pool 5   dialer-group 1   dialer-list 1 protocol ip permit   interface bri 0   encapsulation ppp   dialer pool-member 5   interface serial 0   ip address 192.168.200.1 255.255.255.0   backup interface dialer 1   backup delay 10 20

Dialer Watch Configuration

Define one or more routes or IP addresses to watch:
```
 (global)  dialer watch-list   group-number  [  delay route-check initial   seconds  ]  ip   ip-address mask  
```
A watch list is created with an arbitrary group-number (1 to 255). Each watch-list statement in the list specifies an IP address and a subnet mask to be watched. The IP address given must exactly match a route in the routing table, as shown by the show ip route command. When the primary route to that address is removed from the routing table, the Dialer Watch feature is triggered. The delay route-check initial keywords can be used to force the router to wait for seconds (1 to 2147483 seconds) after the local router powers up and initializes before considering that the primary route is missing.
Select a backup interface:
```
 (global)  interface   type slot/port  
```
This selects the interface to be used by DDR (a logical dialer interface or a physical interface).
Enable Dialer Watch on the backup interface:
```
 (interface)  dialer watch-group   group-number  
```
Dialer Watch uses the Dialer Watch list numbered group-number (1 to 255) to determine when to trigger a DDR call.
(Optional) Wait to disable the backup interface:
```
 (interface)  dialer watch-disable   seconds  
```
After the primary route returns to the routing table, Dialer Watch can wait for seconds (the default is 0 seconds) before disabling the backup DDR call.
Make sure DDR is configured to use the backup interface. Refer to Section 3-3 for more configuration details if needed.

Dialer Watch Example

Dialer Watch is configured so that when the primary route to network 192.168.177.0 or network 192.168.178.0 is deleted from the routing table, DDR uses interface dialer 1 to make a backup connection. Dialer 1 is a logical interface that looks to dialer pool 5 to find an available interface for a new call. Dialer 1 also must have dialer map statements that exactly define the watched routes so that a call can be triggered.

  interface dialer 1   ip address 192.168.1.1 255.255.255.0   encapsulation ppp   dialer map ip 192.168.177.0 5551111   dialer map ip 192.168.178.0 5551111   dialer pool 5   dialer-group 1   dialer watch-group 10   dialer-list 1 protocol ip permit   dialer watch-list 10 ip 192.168.177.0 255.255.255.0   dialer watch-list 10 ip 192.168.178.0 255.255.255.0   interface bri 0   encapsulation ppp   dialer pool-memb   er 5   interface serial 0   ip address ...