remove subinterface

[pccthailand]

Hi

I would like to remove fastethernet subinterface on router that i use to interconnect-vlan . how can i romove it ?

thanks for kindly

[fakabdul]

Hello Rick 

I've faced the symptom as Mohammad, I've created a Sub interface on the router, and tried to deleted using No interface <sub_interface_name>, but when I type show ip int br, i can see the subinterface but in the delete status. 

So from this communicatee as Mohammad saying :- 

Now go through the command as below..

Router(config-if)#int gi0/0/0

Router(config-if)#no interface gi0/0/0.3

and now you will see that 3rd sub interface isn't available anymore.

I did the same steps but this didn't work for, and been forced to reload the router.

[Richard Burts]

Thanks for the clarification. The suggestion to go in config mode first to the physical interface and then to delete the subinterface does not make sense. The command no interface gi0/0/0.3 would work just as well in global config mode as it does in interface mode. And which ever way you do it the subinterface would still show up in the output of show ip interface brief until you reload the router. The only way to get the Ethernet subinterface to not show up in that output is to reload the router.

[Georg Pauwen]

Hello,

what device is this on (e.g. 4331 router) ?

Defaulting the main interface might work:

Router(config-if)#default interface GigabitEthernet0/0/0

[Richard Burts]

Unfortunately defaulting the interface will not achieve the result that show ip interface brief not including the subinterface. Perhaps it will help this discussion if we think about why this is the case. We tend to think about running config as if it were a text file. If it were like a text file then removing the subinterface from the file would not have anything to show up in show ip interface brief. But the running config is a dynamic data structure in the device memory. When we configure the Ethernet subinterface it creates an entry in that dynamic data structure. If we use a config command to remove the subinterface then the entry is deactivated. It no longer shows up in show run (the parser that produces the output is smart enough to skip that data element) but the data element still exists and show ip interface brief will show it. The only way to really eliminate the data structure element is to reload the router.

As a side note it is sometimes possible to completely eliminate a subinterface on a serial interface. I have had the experience of configuring a subinterface of a serial interface for Frame Relay. If things change and I want to eliminate the subinterface, I can use the config command to change the serial interface from Frame Relay to PPP. And then change the interface back to Frame Relay. The result is that show ip interface brief no longer shows the subinterface. Apparently changing the encapsulation of the serial interface completely eliminates existing data structure elements and creates new ones. So it can work for serial interfaces but not for Ethernet interfaces. For Ethernet subinterfaces the only way to get them out of show ip interface brief is to reload. 

[Wizard4777]

Follow these steps:

1. conf t

2. no interface fax/y.nn

3. wr

4. reboot router