Can not enter ip address for Vlan interface

Hi, in router 3925, I want to create vlan 20. After I created it and applied it, I cannot enter ip address in config mode. Please see it below. Any one can give me some suggestion ? Thank you

ERO-(config)#interface vlan
% Invalid input detected at '^' marker.
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Jermaine BhoorasinghJr. Operations EngineerCommented:
If the router doesn't have a switch port module installed then you won't be able to do that.

Are you trying to configure router on a stick? try using a sub-interface
Jermaine BhoorasinghJr. Operations EngineerCommented:
If you are using GNS3 add "NM016ESW" to slot one

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eemoonAuthor Commented:
You are right. I just know that. Thank you.
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