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Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide
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Chapter 13
Configuring Dial Backup and Remote Management
Dial Backup Feature Activation Methods
Note
When static routes are configured, the primary interface protocol must go down in order to activate the
floating static route.
Configuring Floating Static Routes
Static and dynamic routes are the two components of floating static routes. Perform these steps to
configure the static and dynamic routes on your router, beginning in global configuration mode:
Command
Purpose
Step 1
ip route
prefix mask
{
ip-address
|
interface-type
interface-number
[
ip-address
]}
Example:
Router(config)#
ip route 0.0.0.0 0.0.0.0
22.0.0.2
Router(config)#
Assigns the primary static route.
Step 2
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)#
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.
Step 3
router rip
Example:
Router(config)#
router rip
Router(config)#
Enables RIP routing.
Step 4
network
ip-address
Example:
Router(config)#
network 22.0.0.0
Router(config)#
Defines the primary interface network. 22.0.0.0 is
the network value of the primary interface.
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)#
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.
Page 122 / 196
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Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide
OL-5332-01
Chapter 13
Configuring Dial Backup and Remote Management
Dial Backup Feature Activation Methods
Note
When dynamic routes are being used, the time it takes to activate a floating static route depends on the
routing protocol convergence times.
Dialer Watch
The dialer watch method only supports the Extended Interior Gateway Routing Protocol (EIGRP)
link-state dynamic routing protocols.
Configuring Dialer Watch
Perform these steps to configure a dialer watch on your router, beginning in global configuration mode:
Command
Purpose
Step 1
interface
type number
Example:
Router(config)#
interface dialer 2
Router(config-if)#
Enters configuration mode for the dial backup
interface.
Step 2
dialerwatch-group
group-number
Example:
Router(config-if)#
dialer watch-group 2
Router(config-if)#
Specifies the group number for the watch list.
Step 3
exit
Example:
Router(config-if)#
exit
Router(config)#
Enters global configuration mode.
Step 4
ip route
prefix mask
{
ip-address
|
interface-type
interface-number
[
ip-address
]}
Example:
Router(config)#
ip route 0.0.0.0 0.0.0.0
22.0.0.2
Router(config)#
Assigns the primary route. 22.0.0.2 is the peer IP
address of the primary interface.
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Chapter 13
Configuring Dial Backup and Remote Management
Dial Backup Feature Limitations
Dial Backup Feature Limitations
The following limitations exist for the dial backup feature:
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.
Table 13-1
summarizes dial backup support and limitations for the Cisco 800 series access routers.
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)#
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.
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)#
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.
Command
Purpose
Table 13-1
Dial Backup Feature Support and Limitations Summary
WAN Encapsulation
Type
Dial Backup
Possible?
Dial Backup Method
Limitations
Cisco 851 or 871
PPPoE
Yes
Dialer watch
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.
Normal IP in cable
modem scenario
No
Dialer watch
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.
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Chapter 13
Configuring Dial Backup and Remote Management
Dial Backup Feature Limitations
Configuration Example
The following three examples show sample configurations for the three dial backup methods.
Example 13-1
Configuring Dial Backup Using Backup Interfaces
!
vpdn enable
!
vpdn-group 1
accept-dialin
protocol pppoe
!
! Specifies the ISDN switch type
isdn switch-type basic-net3
!
interface vlan 1
ip address 192.168.1.1 255.255.255.0
hold-queue 100 out
!
! ISDN interface to be used as a backup interface
interface BRI0
no ip address
encapsulation ppp
dialer pool-member 1
isdn switch-type basic-net3
!
interface ATM0
backup interface BRI0
no ip address
no atm ilmi-keepalive
pvc 1/40
encapsulation aal5snap
pppoe-client dial-pool-number 2
Cisco 876, 877, or 878
PPP over ATM
PPP over Ethernet
Yes
Backup interfaces
Floating static routes
Dialer watch
Floating static route and dialer watch need a routing protocol
to run in the router. The dialer watch method brings up the
backup interface as soon as the primary link goes down. The
backup interface is brought down as soon as the dialer
timeout is reached and the primary interface is up. The router
checks the primary interface only when the dialer timeout
expires. The backup interface remains up until the dialer
timeout is reached, even though the primary interface is up.
For the dialer watch method, a routing protocol does not need
to be running in the router, if the IP address of the peer is
known.
RFC 1483 (AAL5,
SNAP, and MUX)
Yes
Backup interfaces
Floating static routes
Dialer watch
If bridging is done through the WAN interface, it is not
supported across the auxiliary port.
Table 13-1
Dial Backup Feature Support and Limitations Summary (continued)
WAN Encapsulation
Type
Dial Backup
Possible?
Dial Backup Method
Limitations
Page 125 / 196
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Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide
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Chapter 13
Configuring Dial Backup and Remote Management
Dial Backup Feature Limitations
!
dsl operating-mode auto
!
! Dial backup interface, associated with physical BRI0 interface.
! Dialer pool 1 associates it with BRI0’s dialer pool member 1.
interface Dialer0
ip address negotiated
encapsulation ppp
dialer pool 1
dialer idle-timeout 30
dialer string 384040
dialer-group 1
!
! Primary interface associated with physical ATM0’s interface.
! Dialer pool 2 associates it with ATM0’s dial-pool-number2.
interface Dialer2
ip address negotiated
ip mtu 1492
encapsulation ppp
dialer pool 2
dialer-group 2
no cdp enable
!
ip classless
! Primary and backup interface are given route metric
ip route 0.0.0.0 0.0.0.0 22.0.0.2
ip route 0.0.0.0 0.0.0.0 192.168.2.2 80
ip http server
!
! Specifies interesting traffic to trigger backup ISDN traffic.
dialer-list 1 protocol ip permit
Example 13-2
Configuring Dial Backup Using Floating Static Routes
!
vpdn enable
!
vpdn-group 1
accept-dialin
protocol pppoe
!
! Specifies the ISDN switch type.
isdn switch-type basic-net3
!
interface vlan 1
ip address 192.168.1.1 255.255.255.0
hold-queue 100 out
!
! ISDN interface to be used as a backup interface.
interface BRI0
no ip address
encapsulation ppp
dialer pool-member 1
isdn switch-type basic-net3
!
interface ATM0
no ip address
no atm ilmi-keepalive
pvc 1/40
encapsulation aal5snap
pppoe-client dial-pool-number 2

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