[ASK] Disabled in backup interface???

[Charles_Chi4]

Hi,

I have a problem in configuring two pair of backup interface on my customer's router (3845). It's ok when I configure just one of them. If I configure both pairs of interfaces into backup interface, one of them will be in disabled mode, as shown below :

WANR01#sh ip int bri

Interface                       IP-Address                OK?    Method   Status                             Protocol

GigabitEthernet0/0         172.16.199.106       YES      NVRAM  up                                   up

GigabitEthernet0/1         172.16.3.5              YES      NVRAM  up                                   up

Serial0/0/0                     unassigned            YES      NVRAM  administratively down        down

Serial0/0/1                     unassigned            YES      NVRAM  administratively down        down

FastEthernet0/1/0          125.213.133.186      YES     NVRAM  standby mode                  down

FastEthernet0/2/0          172.112.22.6           YES     NVRAM  standby mode/disabled  down

FastEthernet0/2/1          123.231.177.238      YES     NVRAM  up                                   up

Loopback0                    172.16.199.12          YES     NVRAM  up                                   up    

WANR01#sh backup

Primary Interface   Secondary Interface   Status

-----------------   -------------------   ------

GigabitEthernet0/1  FastEthernet0/2/0     disabled

FastEthernet0/2/1   FastEthernet0/1/0     normal operation

Does anybody have a clue to solve this problem?

[Julio Carvajal]

Hello Peter,

I was just working on a GNS3 lab for the CCIE R&S and got into a task where I should use this kind of Setup redundant interfaces and got the same result ( Got the disabled state).. In my case was because the primary interface was administrative shutdown.

Seems like when this happens the default action is to put the standby interface in shutdown state and it does not matter how many times you get into the backup interface and do a no shut... It will stay on that particular state

I would say that is expected as this works by monitoring the protocol line, not if I have shut it down or not...

Anyway just wanted to share that with anyone else having the same issue, looks like I have hit a wall as it does not matter if I take down the physical link the interface will keep as up. so GNS bug

Regards,

Julio Carvajal

[paul driver]

All,

Just to confirm what Julio/Peter has stated, just tested this on 2811 routers with 12.4T IOS

R1#sh backup

Primary Interface   Secondary Interface   Status

-----------------   -------------------   ------

FastEthernet0/0     FastEthernet0/1       normal operation

Serial0/2/0         Serial0/3/0           normal operation

R1(config)#int ser0/2/0

R1(config-if)#shut

R1#sh backup

Primary Interface   Secondary Interface   Status

-----------------   -------------------   ------

FastEthernet0/0     FastEthernet0/1       normal operation

Serial0/2/0         Serial0/3/0           disabled

res

Paul

Please don't forget to rate any posts that have been helpful.

Thanks.

[Peter Paluch]

Julio and Paul,

I have also re-tested the backup interface feature on a 2691 router IOS. It seems that I have been too hasty in my first answer in this thread. Julio, you have been very kind to mark that answer as Cisco Endorsed but it does not really deserve the rating as it is misleading. I am not sure if you are able to un-mark that designation - if not, I will delete the entire response as it is wrong.

In any case, these are my findings:

• If the main interface is up,up, the backup interface will be put into standby,down mode.
• If the main interface is up,down or down,down, the backup interface will be put into up,up mode.
• If the main interface is administratively down,down, the backup interface will be put into standby/disabled,down
• It is not possible to manipulate the state of the backup interface using the shutdown or no shutdown command. This setting will always be carried over from the main interface.

The last point in particular shows that my former assessment of the situation was wrong. It would not be possible to deactivate the Fa0/2/0 interface as I originally suggested.

So this leaves me puzzled. A backup interface is in disabled state only if the main interface is shutdown. However, the OP's post shows that the main interface Gi0/1 is up,up while the backup interface Fa0/2/0 is disabled. This is clearly not logical. An IOS bug, perhaps?

Best regards,

Peter

[Julio Carvajal]

Hello Peter,

No, there is no way to unmark it,

I got confused with your post Paul lol, I read that you were refiring to the no shut on the pimary interface not the backup one

I would say that if you want we can delete both your answer and mine so we can start from scratch but yes I do agree with you

                STATUS                                                       Protocol

Primary      UP                          UP

Secondary                    Standby mode          Down

Primary                                    Admin down                              Down

Secondary   Standby Disabled    Down

Even if you try to manually do a no shut on secondary or backup interface  it will not come up,

Why?

Because as soon as you configure on the main interface that "x" interface will be backup the status of that interface will depend on the main interface state

Regards

[EminaBrkanic]

I was having the same problem with backup interface. So I just simulate interface to be with line protocol down, and now backup interface is up/up.

regards

[Richard Burts]

Thanks for adding your observation to this old discussion. Your results are consistent with some observations in the discussion. When an interface is configured as backup to some other interface and when the primary interface goes line protocol down then the backup interface does become up/up. But this does not happen if you shut down the primary interface.

HTH

Rick

[ravi rajani]

If we manually shutdown the primary interface, backup interface will go to disabled.
To work it properly, i changed the (serial interface) encapsulation to ppp (other end = hdlc), so for primary interface only protocal went down and backup link became up with below deb logs -

R1(config)#int s1/0
R1(config-if)#enc
R1(config-if)#encapsulation ppp
R1(config-if)#encapsulation ppp
R1(config-if)#end
R1#
R1#
*Mar  1 00:14:27.551: %SYS-5-CONFIG_I: Configured from console by console
R1#
*Mar  1 00:14:27.723: BACKUP(Serial1/0): event = primary interface went down
*Mar  1 00:14:27.727: BACKUP(Serial1/0): changed state to "waiting to backup"
*Mar  1 00:14:28.719: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1/0, changed state to down
R1#
*Mar  1 00:14:28.719: BACKUP(Serial1/0): event = primary interface went down
R1#
*Mar  1 00:14:30.727: BACKUP(Serial1/0): event = timer expired on primary
*Mar  1 00:14:30.731: BACKUP(Serial1/0): secondary interface (Serial1/1) made active
*Mar  1 00:14:30.731: BACKUP(Serial1/0): changed state to "backup mode"
R1#
*Mar  1 00:14:32.727: %LINK-3-UPDOWN: Interface Serial1/1, changed state to up
R1#
*Mar  1 00:14:32.735: BACKUP(Serial1/1): event = secondary interface came up
*Mar  1 00:14:33.731: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1/1, changed state to up
R1#
*Mar  1 00:14:33.731: BACKUP(Serial1/1): event = secondary interface came up
R1#
R1#
R1#
R1#
R1#sh ip int brie
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            unassigned      YES unset  administratively down down
FastEthernet0/1            unassigned      YES unset  administratively down down
Serial1/0                  12.0.0.1        YES manual up                    down
Serial1/1                  120.0.0.1       YES manual up                    up
Serial1/2                  unassigned      YES unset  administratively down down
Serial1/3                  unassigned      YES unset  administratively down down