Dial Backup Feature Limitations - Cisco CISCO851-K9 - 851 Integrated Services Router Configuration Manual

Chapter 13 Configuring Dial Backup and Remote Management
Command
Step 5
ip route prefix mask {ip-address | interface-type
interface-number [ip-address]} [distance]
Example:
Router(config)# ip route 0.0.0.0 0.0.0.0
192.168.2.2 150
Router(config)#
Step 6 dialerwatch-list group-number {ip ip-address
address-mask | delay route-check initial
seconds}
Example:
Router(config)# dialer watch-list 2 ip
22.0.0.2 255.255.255.255
Router(config)#

Dial Backup Feature Limitations

The following limitations exist for the dial backup feature:
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Table 13-1
Table 13-1 Dial Backup Feature Support and Limitations Summary
WAN Encapsulation Dial Backup
Type Possible?
Cisco 851 or 871
PPPoE Yes
Normal IP in cable No
modem scenario
OL-5332-01
Bridging is not supported over console or auxiliary port backup interfaces.
For the Cisco 851 router, only dial-in capability is supported.
Dial backup support on the Cisco 871 router is limited because the Ethernet WAN interface is always
up, even when ISP connectivity is down on the other side of the modem connected to the Cisco 871
router. The router must be in a PPPoE environment with the dialer watch feature running. The IP
addresses of the peer must be specified in the dialer watch and the static route commands to enable
dial backup when the primary line goes down.
summarizes dial backup support and limitations for the Cisco 800 series access routers.
Dial Backup Method
Dialer watch
Dialer watch
Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide
Purpose
Assigns the lower routing administrative distance
value for the backup interface route. 192.168.2.2
is the peer IP address of the backup interface.
Assigns an IP address to the watch list.
If the connection on the primary interface is lost
and the IP address is unavailable on the router, the
dial-out feature on the backup interface is
triggered. 22.0.0.2 is the peer IP address of the
primary interface.
Limitations
Bridging is not supported across a slow interface, for
example, an auxiliary port. The peer IP address of the ISP is
needed to configure the dialerwatch command and the IP
static route.
The IP addresses of the peers are needed for dialer watch to
work properly. If a lease time obtained by DHCP is not set
short enough (1 or 2 minutes), dial backup will not be
supported.
Dial Backup Feature Limitations
13-5