Encapsulation dot1q is not working?, 2600 Cisco router

Question

     I am trying to config a 2620 Cisco router to perform subintreface (F0/0.1) for Vlan Trunk Protocol, however when I try to configure the encapsulation dot1q, I continue to receive error massage with ^ symbol below the 'c' See below, the platform version is a 12.3(26) which should be acceptable to perform an (encapsulation dot1q). The Ethernet is a fast-Ethernet 10/100 port. I also try the ISL, I receive the same massage.
Can anyone suggest what could be the problem!! 
Thank you all!!!!!
Router#config t
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#int f0/0
Router(config-if)#no ip address
Router(config-if)#no shutdown
Router(config-if)#int f0/0.1
Router(config-subif)#encapsulation dot1q 1                     
^ % Invalid input detected at '^' marker. Router(config-subif)#
==================================================================================================== Router#show version
Cisco Internetwork Operating System Software IOS (tm) C2600 Software (C2600-I-M), Version 12.3(26), RELEASE SOFTWARE (fc2) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2008 by cisco Systems, Inc. Compiled Mon 17-Mar-08 15:23 by dchih ROM: System Bootstrap, Version 12.1(3r)T2, RELEASE SOFTWARE (fc1) Router uptime is 5 minutes System returned to ROM by power-on System image file is "flash:c2600-i-mz.123-26.bin" cisco 2620 (MPC860) processor (revision 0x600) with 28672K/4096K bytes of memory . Processor board ID JAD05440GAN (1508240486) M860 processor: part number 0, mask 49 Bridging software. X.25 software, Version 3.0.0. 1 FastEthernet/IEEE 802.3 interface(s) 1 Serial network interface(s) 32K bytes of non-volatile configuration memory. 8192K bytes of processor board System flash (Read/Write)
Configuration register is 0x2102
Router#
==================================================================================================
Router#sh flash
System flash directory:
File  Length  Name/status  
1  7754580  c2600-i-mz.123-26.bin [7754644 bytes used, 633960 available, 8388604 total]
8192K bytes of processor board System flash (Read/Write)
Router#

Answer 1

jesse rodriguez wrote:I am connected through the console, Here are the output.Router#config t Enter configuration commands, one per line.  End with CNTL/Z. Router(config)# Router(config)# Router(config)#int f0/0 Router(config-if)#no ip address Router(config-if)#no shutdown Router(config-if)# *Mar  1 00:01:36.891: %LINK-3-UPDOWN: Interface FastEthernet0/0, changed state t o up Router(config-if)# Router(config-if)#int f0/0.1Router(config-subif)#enc ? % Unrecognized commandRouter(config-subif)#en? % Unrecognized command Router(config-subif)#en ? % Unrecognized command Router(config-subif)#enJesse
It's possible your feature set it not good enough to run trunking.
Trunking apparently requires a minimum of the IP PLUS feature set according to this document
http://www.cisco.com/en/US/tech/tk389/tk815/technologies_configuration_example09186a00800949fd.shtml
table 2 shows a minimum IOS of 12.0(1)T and IPPLUS/IPPLUS on the 2620 - so your IOS revision is OK, but maybe your feature set is not.
You can figure which feature set you have by going here
http://tools.cisco.com/ITDIT/CFN/Dispatch?act=rlsSelect&task=search&searchby=image
and entering your image name (assuming it's not been stuffed with) which you can find by doing "show flash" or "dir"
If you don;t have the right feature set, then you're out of luck unless you can upgrade/change the IOS image the router is booting with.
Cheers.