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New Member

Backup interface on fiber ring

We recently installed a 100Meg MPLS fiber ring into our office, and we were given redundant connections (north loop and south loop).


The North loop is the primary interface, and will be used unless the fiber is cut.


I need to configure our router to automatically switch to the south loop in the event that the north loop goes down. 


Here is the config I have so far, I just want to make sure I'm not missing anything.


interface GigabitEthernet0/0/0
 description 100MB MPLS North Loop
  backup delay 30 never
 backup interface GigabitEthernet0/0/1
 ip address X.X.X.X
 media-type sfp
 negotiation auto
interface GigabitEthernet0/0/1
 description 100MB MPLS backup South Loop
 ip address X.X.X.X
 media-type sfp
 negotiation auto

Am I correct in thinking that, should the North loop on Gi0/0/0 go down, it will automatically switch to Gi0/0/1 after 30 seconds of down time?


If so, how do I go about switching back to the north loop when it comes back online?


Cisco Employee

Hi,I have see this feature


I have see this feature configure on few ISP. For this feature to work, interface needs to go down then only RP can send UP event to standby link and make it up. 

You can also go through below discussion on backup interface


regarding backup delay , i am not sure why you want to put delay of 30 sec before standby interface becomes active and then deactivating delay is infinite, means it will always remain active even when primary interface comes up.


CCO document on backup delay


backup delay

To define how much time should elapse before a secondary line status changes after a primary line status has changed, use the backup delaycommand in interface configuration mode. To return to the default so that as soon as the primary fails, the secondary is immediately brought up without delay, use the no form of this command.

backup delay {enable-delay-period | never} {disable-delay-period | never}

no backup delay {enable-delay-period | never} {disable-delay-period | never}

Syntax Description



Number of seconds that elapse after the primary line goes down before the Cisco IOS software activates the secondary line.


Number of seconds that elapse after the primary line comes up before the Cisco IOS software deactivates the secondary line.


Secondary line is never activated or deactivated.




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