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Dialer Watch is a backup feature that integrates dial backup with routing capabilities. Prior dial backup implementations used the following conditions to trigger backup:
Prior backup implementations may not have supplied optimum performance on some networks, such as those using Frame Relay multipoint subinterfaces or Frame Relay connections that do not support end-to-end PVC status updates.
Dialer Watch provides reliable connectivity without relying solely on defining interesting traffic to trigger outgoing calls at the central router. Dialer Watch uses the convergence times and characteristics of dynamic routing protocols. Integrating backup and routing features enables Dialer Watch to monitor every deleted route. By configuring a set of watched routes that define the primary interface, you are able to monitor and track the status of the primary interface as watched routes are added and deleted. Monitoring the watched routes is done in the following sequence:
1. Whenever a watched route is deleted, Dialer Watch checks to see if there is at least one valid route for any of the defined watched IP addresses.
2. If no valid route exists, the primary line is considered down and unusable.
3. If a valid route exists for at least one of the defined IP addresses, and if the route is pointing to an interface other than the backup interface configured for Dialer Watch, the primary link is considered up.
4. In the primary link goes down, Dialer Watch is immediately notified by the routing protocol and the secondary link is brought up.
5. Once the secondary link is up, at the expiration of each idle timeout, the primary link is rechecked.
6. If the primary link remains down, the idle timer is indefinitely reset.
7. If the primary link is up, the secondary backup link is disconnected. Additionally, you can set a disable timer to create a delay for the secondary link to disconnect, after the primary link is reestablished.
Dialer Watch provides the following advantages:
dial-on-demand routing (DDR)---Technique whereby a router can automatically initiate and close a circuit-switched session as transmitting stations demand. This demand is based on predefined variables configured on the router. The router spoofs keepalives so that end stations treat the session as active. DDR permits routing over ISDN or telephone lines that use an external ISDN terminal adaptor (TA) or modem.
International Telecommunication Union Telecommunication Standardization Sector (ITU-T)---International body that develops worldwide standards for telecommunications technologies.
V.25bis---ITU-T specification describing the procedures for call setup and tear down over the public switched data network (PSDN).
watched network---Network(s) or specific addresses (routes) that Dialer Watch monitors for connectivity loss.
This feature is supported on these platforms:
The following prerequisites apply to Dialer Watch:
For information on how to configure traditional DDR for dial backup, refer to the "Dial Backup" chapter in the Dial Solutions Configuration Guide for Cisco IOS Release 11.3.
Perform the following tasks to configure Dialer Watch. All tasks are required except the last task to set a disable timer.
Decide which interfaces on which routers will act as primary and secondary interfaces. Unlike traditional backup methods, you can now define multiple interfaces on multiple routers, instead defining a single interface on the router.
Determine which addresses and networks are to be monitored or watched. Typically, what is watches is an interface on a remote router or a network advertised by a central or remote router.
To initiate Dialer Watch, you must configure the interface to perform DDR and backup. Use traditional DDR configuration commands, such as dialer maps, for DDR capabilities. To enable Dialer Watch on the backup interface, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Enable Dialer Watch on the backup interface. | dialer watch-group group-number |
To define the IP addresses you want watched, perform the following task in global configuration mode:
| Task | Command |
|---|---|
Define all IP addresses to be watched. | dialer watch-list group-number ip ip-address address-mask |
The dialer watch-list command is the means to detect if the primary interface is up or down. The primary interface is determined to be up when there is an available route with a valid metric to any of the addresses defined in this list, and it points to an interface other than the interface on which the dialer watch-group is defined. The primary interface is determined to be down when there is no available route to any of the addresses defined in the dialer watch-list command.
This task is optional. Under some conditions, you may want to set an alternative delay between the time the primary interface recovers and the time the backup interface is dropped. This delay can ensure stability, especially for flapping interfaces or interfaces experiencing frequent route changes. To set the delay, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Set a delay time to the interface. | dialer watch-disable seconds |
In the following example, Pioneer and Hubble are connected via Frame Relay. Magellon is configured to perform Dialer Watch, and it will watch networks 3.0.0.0, 4.0.0.0, and 5.0.0.0. If routing updates are deleted for these three networks, Magellon will implement Dialer Watch by initiating the call to Pioneer. Comments precede the configuration commands and are noted by an exclamation mark (!). Refer to Cisco IOS Release 11.3 configuration guides and command references for additional information on configuring Frame Relay, PPP, and traditional dial backup features. Figure 1 shows Dialer Watch configured to backup primary interfaces that are configured for Frame Relay.
interface Ethernet0
! Hubble and magellon are on same LAN
ip address 172.21.24.85 255.255.255.0
interface serial1
! This is the Primary multipoint interface
ip address 3.1.1.1 255.255.255.0
encapsulation frame-relay
frame-relay map ip 3.1.1.1 100
frame-relay map ip 3.1.1.2 200
frame-relay map ip 3.1.1.3 300
! The interfaces are configured to use EIGRP routing
router eigrp 190
network 3.0.0.0
network 172.21.0.0
!
end
! Remote site username and shared password. Password is not encrypted to show
! that thepassword is shared between the routersusername pioneer password starz
interface Ethernet0
! This is in the same LAN as Hubble Ethernet 0
ip address 172.21.24.86 255.255.255.0
!
interface bri0
! This is the secondary backup line
ip address 7.1.1.2 255.255.255.0
encapsulation ppp
dialer idle-timeout 5
! Use a dialer map for the IP address/network which is the same network as
! being watched
dialer map ip 3.1.1.0 name pioneer 60079 broadcast
! Add a dialer map for remote end's IP address to make routing work over this
interface
dialer map ip 7.1.1.3 name pioneer 60079 broadcast
dialer-group 1
! Enable Dialer Watch on this interface
dialer watch-group 1
ppp authentication chap
!
! The interfaces are configured to use EIGRP routing
router eigrp 190
network 7.0.0.0
network 172.21.0.0
!
access-list 100 deny eigrp any any
access-list 100 permit ip any any
! Watch IP networks 3.1.1.0, 4.1.1.0, and 5.1.1.0
dialer watch-list 1 ip 3.1.1.0 255.255.255.0
dialer watch-list 1 ip 4.1.1.0 255.255.255.0
dialer watch-list 1 ip 5.1.1.0 255.255.255.0
dialer-list 1 protocol ip list 100
!
end
! Remote site username and shared password. Password is not encrypted to show that
! the password is shared between the routersusername magellon password starz
interface ethernet0
ip address 182.21.75.21 255.255.255.0
interface serial1
! This is Primary interface on the remote end
ip address 3.1.1.2 255.255.255.0
encapsulation frame-relay
frame-relay map ip 3.1.1.1 100
!
interface bri0
! This is where the secondary dials in. This router does not require a dialer map
! statement because it is receiving the call.
ip address 7.1.1.3 255.255.255.0
encapsulation ppp
! The dialer idle-timeout command prevents premature hangup
dialer idle-timeout 10000
dialer-group 1
ppp authentication chap
!
access-list 100 permit ip any any
dialer-list 1 protocol ip list 100
!
! The interfaces are configured to use EIGRP routing
router eigrp 190
network 3.0.0.0
network 7.0.0.0
network 182.21.0.0
!
end
This section documents new commands required to configure the Dialer Watch feature. All other commands used with this feature are documented in the Dial Solutions Command Reference for Cisco IOS Release 11.3.
To set a delay time to the backup interface, use the dialer watch-disable interface configuration command. At times, you may want to delay disconnecting the backup interface after the primary interface recovers. To disable this feature, use the no form of this command.
dialer watch-disable seconds
seconds | The timeout value in seconds. |
Disabled
Interface configuration
This command first appeared in Cisco IOS Release 11.3T.
This command is optional.
This command is used to add a delay time to the backup interface. The delay time delays the time it takes for the backup interface to disconnect after the primary interface recovers.
The following example forces a 6-second delay to the backup interface once the primary interface recovers:
interface bri0 ip address 2.1.1.2 255.255.255.0 encapsulation ppp dialer map ip 3.1.1.1 255.255.255.0 name hubble 5551234 dialer-group 1 dialer watch-group 1 dialer watch-disable 6
show dialer interface
To enable DDR backup on an interface using Dialer Watch, configure the interface using the dialer watch-group interface configuration command. To disable this feature, use the no form of this command.
dialer watch-group group-number
group-number | Group number assigned that will point to a globally defined list of IP addresses to watch. The valid range is 1 to 255. |
Disabled
Interface configuration
This command first appeared in Cisco IOS Release 11.3T.
Use the dialer watch-group command on the secondary interface you want to enable DDR backup.
The dialer watch group number points to a globally defined list (the dialer watch-list command) that contains the IP addresses to be watched. If you use the dialer watch-group command you must also use the dialer watch-list command.
You must configure the standard commands required to enable the router to perform DDR in addition to the Dialer Watch commands. Refer to Cisco IOS Release 11.3 configuration guides and command references for additional information.
The dialer watch-group and dialer watch-list commands can be added in any order.
The following example configures BRI interface 0 as the backup interface:
interface bri0
ip address 2.1.1.2 255.255.255.0
encapsulation ppp
dialer watch-group 1
To add the list of IP addresses you want monitored, use the dialer watch-list global configuration command. To disable this feature, use the no form of this command.
dialer watch-list group-number ip ip-address address-mask
group-number | Group number assigned to the list. Valid group numbers are between 1 and 255. |
ip | IP is the only routed protocol supported for Dialer Watch at this time. |
ip-address | IP address or address range to be applied to the list. |
address-mask | IP address mask to be applied to the list. |
Disabled
Global configuration
This command first appeared in Cisco IOS Release 11.3T.
Use this command to add all IP addresses or networks you want monitored.
There is no software limit to the number of protocol addresses that can be added to the group.
Address matching is exact; therefore, you must apply the specific IP address and mask range for the networks you want monitored.
Use this command with the dialer watch-group interface configuration command. The number of the group list must match the group number. For example, if you use dialer watch-group number 1, you must also use dialer watch-list number 1.
You must configure the standard commands required to enable the router to perform DDR in addition to the Dialer Watch commands. Refer to Cisco IOS Release 11.3 configuration guides and command references for additional information.
The dialer watch-list and dialer watch-group commands can be added in any order.
The following example adds the IP addresses to be watched:
dialer watch-list 1 ip 3.1.1.0 255.255.255.0
dialer watch-list 1 ip 2.1.1.0 255.255.255.0
dialer watch-list 1 ip 5.1.1.0 255.255.255.0
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