How to always keep 3G connection up as backup?

[dennis_range]

I have many HWIC-3G-HSPA cards as backup connections and I need to keep them up for monitoring purposes. Being a backup connection they get little interesting traffic for them to spring into life but they are the source interface for a tunnel interface (we use DMVPN). The interface still insists on going down. I have even added static routes to the DMVPN hubs over the cellular interface and they still go down. What command do I enter to always keep them up? I had originally used 'dialer idle-timeout 0' and then removed it altogether which the same results. Below is what I have now.

interface Cellular0/1/0
ip address negotiated
ip nat outside
ip virtual-reassembly in
encapsulation ppp
dialer in-band
dialer string gsmscript
dialer-group 1
async mode interactive
ppp chap hostname //username//
ppp chap password //password//

ppp ipcp dns request

access-list 1 permit any
dialer-list 1 protocol ip list 1

line 0/1/0
exec-timeout 0 0
script dialer gsmscript
modem InOut
no exec
transport input all
transport output all
rxspeed 7200000
txspeed 5760000

[Matteo Comisso]

Hi Dennis,

I had the same problem and, thanks to uncle Google, I've found the solution

This is the final config:

Router#sh run    

Building configuration...

Current configuration : 2120 bytes
!
! Last configuration change at 12:04:38 UTC Mon Nov 14 2011
version 15.1
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname Router
!
boot-start-marker
boot-end-marker
!
!
!
no aaa new-model
!
dot11 syslog
ip source-route
!
!
!
!
!         
ip cef
ip name-server 208.67.222.222
ip name-server 208.67.220.220
ip ddns update method ddns
 HTTP
  add http://username:password@members.dyndns.org/nic/update?hostname=password@members.dyndns.org/nic/update?hostname=&myip=
  remove http://username:password@members.dyndns.org/nic/update?hostname=password@members.dyndns.org/nic/update?hostname=&myip=
 interval maximum 0 1 0 0
!
!
multilink bundle-name authenticated
!
chat-script gsm "" "ATDT*99#" TIMEOUT 60 "CONNECT"
crypto pki token default removal timeout 0
!
!
!
!
license udi pid CISCO2801 sn FCZ102213BX
!
redundancy
!         
!
controller Cellular 0/1
!
! 
!
!
!
!
!
!
interface FastEthernet0/0
 ip address 192.168.0.1 255.255.255.0
 ip nat inside
 ip virtual-reassembly in
 duplex auto
 speed auto
!
interface FastEthernet0/1
 no ip address
 shutdown
 duplex auto
 speed auto
!
interface Cellular0/1/0
 no ip address
 ip nat outside
 ip virtual-reassembly in
 encapsulation ppp
 dialer in-band
 dialer pool-member 1
 async mode interactive
 ppp chap hostname 
 ppp chap password 0 
 ppp ipcp dns request
!
interface Cellular0/1/1
 no ip address
 encapsulation ppp
!
interface Dialer1
 ip ddns update hostname myhostname.dyndns.org
 ip ddns update ddns
 ip address negotiated
 ip nat outside
 ip virtual-reassembly in
 encapsulation ppp
 dialer pool 1
 dialer idle-timeout 0
 dialer string gsm
 dialer persistent
 no cdp enable
!
ip forward-protocol nd
!
!
no ip http server
no ip http secure-server
ip nat inside source list 10 interface Dialer1 overload
ip route 0.0.0.0 0.0.0.0 Dialer1
!
access-list 1 permit any
dialer-list 1 protocol ip list 1
!
!
!
!
!
control-plane
!
!
!
line con 0
line aux 0
line 0/1/0
 exec-timeout 0 0
 script dialer gsm
 login
 modem InOut
 no exec
 rxspeed 7200000
 txspeed 2000000
line 0/1/1
 no exec
 rxspeed 7200000
 txspeed 2000000
line vty 0 4
 login
 transport input all
!
scheduler allocate 20000 1000
end

Thanks to the "dialer persistent" parameter, that has to be put into the dialer interface, the cellular line is always up!

Regards,

Matteo