I follow a tutorial, there shows the method of create sub-interface:

but in my actual situation, I can not do this:

Router(config)#interface gigabitEthernet 2/1.100
% Invalid input detected at '^' marker.

my router is CGR 1240 in Cisco Packet Tracer.

  • 1
    You cant expect packet tracer to give all the real world functionalities.
    – user36472
    Nov 7, 2018 at 6:34
  • are all the routers can not create sub interfaces?
    – 244boy
    Nov 7, 2018 at 6:45
  • i dont remember, but i dont think they can.
    – user36472
    Nov 7, 2018 at 6:59
  • Did the answer help you? If so you should accept the answer so that it does not keep popping up. Alternatively you can add your own answer and accept that.
    – user36472
    Nov 15, 2018 at 10:15

1 Answer 1


The GCR routers do not support the sub-interface in Packet tracer, you can change your router to a high-level router, such as ISR4321, then you can create easily for experiment:

RT1(config)#interface gigabitEthernet 0/0/0.100 
%LINK-5-CHANGED: Interface GigabitEthernet0/0/0.100, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0/0.100, changed state to up

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