Cisco intervlan routing

Posted on 2009-04-09
Last Modified: 2012-05-06

I'm currently studying for my CCNA 640-802 and I am working in a lab with a cisco 2950 24 port switch and a 2600 router. I am trying to set up intervlan routing, and have entered the following

RouterA#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
RouterA(config)#int fa0/0
RouterA(config-if)#no shut
00:05:03: %LINK-3-UPDOWN: Interface FastEthernet0/0, changed state to up
00:05:04: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up
RouterA(config-if)#int fa0/0.1
RouterA(config-subif)#ip address

Configuring IP routing on a LAN subinterface is only allowed if that
subinterface is already configured as part of an IEEE 802.10, IEEE 802.1Q, or ISL vLAN.


Not sure what else to do here? I am following the guide I have in a lab book, even the encapsulation dot1q command will not work on the sub interface.

Question by:cheesebugah
  • 3
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Author Comment

ID: 24111239
RouterA(config-subif)#encapsulation dot1q 20
% Invalid input detected at '^' marker.


Expert Comment

ID: 24111363
You output gave you an error in the prompt. That should not be happening unless you were typing in the prompt.

RouterA(config-subif)#encapsulation dot1q 20

Just to verrify, You are typing in:
int fa0/0.1
encapsulation dot1q 20


Author Comment

ID: 24111416

RouterA(config-subif)#encapsulation dot1q 20

is where the error is. I am on IOS v12.0(7)
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Accepted Solution

Sniper98G earned 250 total points
ID: 24112165
OK that's your problem. 12.0 does not support 802.1q encapsulation; 802.1q became available in 12.2. Also; since the 2950 you are using only supports 802.1q you cannot use ISL. The only option you have is to upgrade the router with a later IOS.

Expert Comment

ID: 24113123
also make sure your IOS is not a basic ip services IOS, those won't include dot1q either.

Author Closing Comment

ID: 31568732
That's what I was afraid of. We purchased a CCNA/NP Lab on ebay, its 3 2950 switches, 2 2600 routers, and 2 3400 routers.... I think I know where I can find 12.4 IOS... thanks again!

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