- Enterasys Security Router User's Guide

Dialer Watch
XSR User’s Guide 10-19
A watch group can also be specified for use by the Virtual Router Redundancy Protocol (VRRP)
with the
vrrp <number> track watch-group command. 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
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.
192.144.2.0
Leased line (T1)
5.5.5.0
2nd ISDN Backup line
1.1.1.0
192.100.3.0
Router D
Primary leased line (T1)
20.20.20.0
Leased line (T1)
192.168.27.0
1st ISDN Backup line
10.10.10.0
Watched routes:
192.144.2.0
192.168.27.0
192.100.3.0
Router B
Router C
Router A
3.3.3.0