Problem with "encapsulation dot1q" on 2621/2620 Router

Unanswered Question
Feb 19th, 2007

Hey all,

I am assisting the Cisco CCNA semester 3 students with a lab. The students are using the white and green CCNA 3 and 4 Lab Companion Third Edition book. I am on page 171 step B. When I get to the step to configure the router with "encapsulation dot1q 1", I get an invalid command error. The encapsulation option does not even show up in the ? list. Any thoughts? The only thing I can think of is the IOS version. The other 2600's in our lab do the same thing. Please see the attached file for a copy/paste of the commands that were input, including a sh run.

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (2 ratings)
sachinraja Mon, 02/19/2007 - 18:04

Hello Tavis

You must be running the IP base version of IOS... for trunking to be supported, you must need atleast IP Plus version !!! If you have access to the software advisor on CCO, you can get a list of IOS which supports trunking. You can also include the features you want and get the IOS versions...

Hope this helps.. all the best...


sachinraja Mon, 02/19/2007 - 18:10

Hello Tavis,

I just ran the software advisor, and it gave the following results (for dot1q trunking support):

1) c2600-ipbase-mz.12.3-4.XD1 - (not sure if available for download)

2) c2600-is-mz.12.3-22 - available for download

3) c2600-is-mz.12.2-15.T7 - available

the IOS requires atleast 64 MB DRAM and 32 MB Flash..

Hope this helps.. all the best.. rate replies if found useful..


Tavis10284 Mon, 02/19/2007 - 18:39

Thanks for your quick replies and confirmation that it was the IOS that was the issue, Raj.

I have these IOS images on hand:




I will try these on one of the 2600 routers tomorrow and see if it will work.

sachinraja Mon, 02/19/2007 - 18:48

Hello Tavis,

Try the second IOS (IP Plus) and it will work. I just checked your software on the tool, and it gave dot1q trunking support for it. I'm really not sure if it will be enabled for the IP Base IOS that you have given... If you have sufficient DRAM and flash, please go for the is-mz-122.24a image...


petrokast Wed, 11/20/2013 - 11:09

Hi Raj,

Thanks ever so much! Tried various IOS images which sort of should've supported encapsulation and none of those had the encapsulation functionality... Luckily I found this post, changed the IOS image to c2600-is-mz.12.3-22  and voila! Can carry on with my lab!!!

On the other hand - had very interesting experience uploading IOS files to flash

Thanks again!




This Discussion