Cisco BackUp Interface Operation Failing

Question

OK Experts,
I have made this issue very simple for you guys to help me out.
I  have two routers R22 and R23. I have configured the back up interface  on R22 to be interface fas 0/1. Everything appears to be working fine. I  issue the command show backup and I get the following on R22
r22#show backup
Primary Interface   Secondary Interface   Status
FastEthernet0/0     FastEthernet0/1       normal operation
r22#
Also I get the following:
FastEthernet0/1            10.10.13.2      YES manual standby mode          down
However, when I shutdown interface fast 0/0 to test the back up interface fast 0/1 I get the following:
r22#show backup
Primary Interface   Secondary Interface   Status
FastEthernet0/0     FastEthernet0/1       disabled
r22#
FastEthernet0/1            10.10.13.2      YES manual standby mode/disabled down
So it doesn't work.
Attached are the configs.
I was wondering if someone could help me figure out why this won't work.
Cheers

Answer 1

Hello Carlton,
there are some notes about your tests:
a)  the configuration of the primary interface includes two logical interfaces main interface and a vlan based subinterfaces both fail when you disable fas0/0, the secondary interface has only IP configuration at main interface level
from your log files:
interface FastEthernet0/0
backup interface FastEthernet0/1
ip address 10.10.14.2 255.255.255.0
duplex auto
speed auto
interface FastEthernet0/0.1
encapsulation dot1Q 12
ip address 10.10.12.2 255.255.255.0
You should remove the subinterface fas0/0.1 as a minimum to make interface configurations compatible,
b) the specific type of interface you  would like to use for backup is LAN based Fastethernet.
The backup command had been introduced for providing a backup interface for serial interface and the secondary interface may be a serial interface or ISDN based ( in this case a DDR call is triggered over ISDN).
The dial backup command reference says that support for gigabit interfaces in C7600 has been later introduced.
see
http://www.cisco.com/en/US/docs/ios/dial/command/reference/dia_a1.html#wp1012054
The use of backup command may be supported or not for fastethernet interface on your routers.
If it is not supported, you can easily implement an alternate solution, because you are running OSPF in area 0 in all router interfaces
router ospf 1
log-adjacency-changes
>>network 0.0.0.0 255.255.255.255 area 0
So all you need to do  is to increase OSPF cost on fas0/1 to create a backup path
on R22, R23:
conf t
interface fas0/1
ip ospf cost 50
Hope to help
Giuseppe