Cisco CCNA CCNP Certification Exam Tutorial Dialer Watch
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Cisco CCNA/CCNP Certification Exam Guide: Understanding Dialer Watch
Overview:
Dialer Watch is a key concept in Cisco's CCNA and CCNP certification exams, especially in the BCRAN module. It's crucial to grasp this technology and avoid common mistakes to succeed. Here, expert Chris Bryant, CCIE
12933, provides a comprehensive guide to Dialer Watch.
Understanding Dialer Watch:
Dialer Watch is a configuration that allows routers to monitor specified routes. If a "watched" route disappears from the routing table and no alternative exists, the ISDN link automatically activates. This setup ensures connectivity through backup links when primary paths fail.
Example Setup:
Consider two routers, R1 and R2, connected through a Frame Relay cloud on the 172.12.123.0/24 network and an ISDN cloud on 172.12.12.0/24. OSPF is running over the Frame Relay, with R1 advertising its loopback (1.1.1.1/32) and an Ethernet segment (10.1.1.0/24) via OSPF. R2 maintains these routes in its OSPF table:
```
R2
show ip route ospf
1.0.0.0/32 is subnetted, 1 subnets
O 1.1.1.1 [110/65] via 172.12.123.1, 00:00:07, Serial0
10.0.0.0/24 is subnetted, 1 subnets
O 10.1.1.0 [110/128] via 172.12.123.1, 00:00:08, Serial0
```
Configuring Dialer Watch:
1. Create a Watch List:
Use `dialer watch-list` to define the routes to monitor. If any route in this list leaves the routing table, the ISDN link triggers.
```shell
R2(config)
dialer watch-list 5 ip 10.1.1.0 255.255.255.0
R2(config)dialer watch-list 5 ip 1.1.1.1 255.255.255.255
```Note: Ensure route entries match exactly with subnet masks.
2. Set Up Watch Group:
Assign the watch group to the BRI interface using `dialer watch-group`. Ensure the group number matches the watch-list:
```shell
R2(config)
interface bri0
R2(config-if)dialer watch-group 5
```3. Frame Map Statements:
Essential for Dialer Watch, frame map statements are required for each route.
```shell
R2(config-if)
dialer map ip 1.1.1.1 255.255.255.255 name R1 5557777 broadcast
R2(config-if)dialer map ip 10.1.1.0 255.255.255.0 name R1 5557777 broadcast
```Testing Dialer Watch:
- Shut down the Serial0 interface on R2. The change in OSPF's route table should immediately trigger the ISDN link:
```shell
R2(config)
int s0
R2(config-if)shut
```- Observe the logs confirming the ISDN link activation.
- Validate using `show dialer`:
```shell
R2
show dialer
Dialer state is data link layer upDial reason: Dialing on watched route loss
```
Final Considerations:
Dialer Watch is compatible with dynamic IGPs like IGRP, EIGRP, and OSPF, but not with RIP. Proper configuration of Dialer Watch ensures reliable backup connectivity, enhancing network resilience.
By mastering Dialer Watch, you're better prepared to tackle your Cisco certification exams with confidence.
You can find the original non-AI version of this article here: Cisco CCNA CCNP Certification Exam Tutorial Dialer Watch.
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