Enterasys Networks X-PeditionTM manual Dialer Watch Behavior, Dialer Watch Topology

Dialer Watch

A watch group can also be specified for use by the Virtual Router Redundancy Protocol (VRRP) with the vrrp <number> track watch-groupcommand. For more information, refer to “Configuring IP” on page 1.

At the outset, the XSR’s Routing Table Manager (RTM) notifies the Dialer subsystem when a route is added or deleted from the routing table. Then, based on the configuration, the Dialer decides to start backup using a preconfigured profile including information such as the dialer string, dialer pool, IP address, and other values as described in this chapter.

In the star topology illustrated in Figure 10-9, Routers A, B, C and D have connectivity to all peers through primary leased lines. Whenever one or two of the primary connections go down, Router A will re-establish total connectivity by bringing up one or two backup switched lines.

Figure 10-9 Dialer Watch Topology

192.144.2.0
Router D		2nd ISDN Backup line
		1.1.1.0
Leased line (T1)	192.100.3.0
5.5.5.0
			Router A
Router B		Primary leased line (T1)
		20.20.20.0	Watched routes:
Leased line (T1)
			192.144.2.0
3.3.3.0
			192.168.27.0
		ISDN Backup line	192.100.3.0
Router C		10.10.10.0
192.168.27.0

Dialer Watch Behavior

The XSR performs Dialer Watch monitoring in the following sequence:

•Whenever a watched route is deleted, Dialer Watch checks to see if there is at least one valid route for the defined watched IP address

•If no valid route exists, the primary line is considered down and unusable.

•If a valid route exists for the at least one defined IP address on the watch list, and if the route is pointing to an interface other than the backup interface configured for Dialer Watch, the primary link is considered up.

•If the primary link goes down, Dialer Watch is immediately notified by the routing protocol and the secondary link brought up.

•If the primary link remains down, the secondary link stays up indefinitely.

•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 re-established.

XSR User’s Guide 10-19