I've got a brand new cisco router 3925/k9. I wanted to set up a router on a stick on my network, but it turns out it doesn't support vlan sub-interfaces. I did it multiple times in gns3 simulator on other routers, so I am familiar with IOS commands and concepts. I believe this must be a licensing issue, but so far I couldn't find anything on cisco website that explains it. Here is some info from "show version":

ROM: System Bootstrap, Version 15.0(1r)M13, RELEASE SOFTWARE (fc1)
System image file is "flash0:c3900-universalk9-mz.SPA.151-4.M2.bin"
3 Gigabit Ethernet interfaces
1 terminal line
1 Virtual Private Network (VPN) Module
DRAM configuration is 72 bits wide with parity enabled.
255K bytes of non-volatile configuration memory.
250880K bytes of ATA System CompactFlash 0 (Read/Write)

License Info:
Technology    Technology-package           Technology-package
              Current       Type           Next reboot
ipbase        ipbasek9      Permanent      ipbasek9
security      securityk9    Permanent      securityk9
uc            None          None           None
data          None          None           None

I would appreciate if anyone could give me a clue what I can do to enable vlan support on this router.

  • Why haven't you just asked Cisco Tech Support? – the-wabbit Feb 6 '12 at 21:11
  • 1
    According to the feature navigator your router should support 802.1q VLANs. What config are you trying to enter? Is it encapsulation dot1q <xx> under the subinterface? – resmon6 Feb 7 '12 at 14:57

cisco router 3925/k9 fully supports 802.1q VLANs. The problem was lack of my attention. I totally forgot that encapuslation dot1q is available in subinterface and not the main interface. so the correct config for enabling vlans on cisco router should look like this:

Router_A(config)#interface fastethernet 0/0
Router_A(config-if)#no shutdown
Router_A(config-if)#interface fastethernet 0/0.1
Router_A(config-subif)#encapsulation dot1q 1
Router_A(config-subif)#ip address
Router_A(config-if)#interface fastethernet 0/0.2
Router_A(config-subif)#encapsulation dot1q 10
Router_A(config-subif)#ip address
Router_A(config-if)#interface fastethernet 0/0.3
Router_A(config-subif)#encapsulation dot1q 20
Router_A(config-subif)#ip address

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