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New Member

Encapsulation command in subif


I have a 2610 router and I am attempting to enable DOT1Q on eth0/0.1 for router-on-a-stick configuration.

My sh ver is as follows:

Router>sh ver

Cisco Internetwork Operating System Software

IOS (tm) C2600 Software (C2600-I-M), Version 12.2(8)T5, RELEASE SOFTWARE (fc1)

TAC Support:

Copyright (c) 1986-2002 by cisco Systems, Inc.

Compiled Fri 21-Jun-02 08:50 by ccai

Image text-base: 0x80008074, data-base: 0x80A2BD40

ROM: System Bootstrap, Version 11.3(2)XA4, RELEASE SOFTWARE (fc1)

Router uptime is 39 minutes

System returned to ROM by reload

System image file is "flash:c2600-i-mz.122-8.T5.bin"

cisco 2610 (MPC860) processor (revision 0x203) with 28672K/4096K bytes of memory.

Processor board ID JAD042108TF (1440777694)

M860 processor: part number 0, mask 49

Bridging software.

X.25 software, Version 3.0.0.

1 Ethernet/IEEE 802.3 interface(s)

32K bytes of non-volatile configuration memory.

8192K bytes of processor board System flash (Read/Write)

Configuration register is 0x2102


Now the problem is I can not enter the encapsulation command as you can see here:

Router#conf t

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)#int eth0/0.1



% Invalid input detected at '^' marker.

Any reason for this? I thought IOS 12.2 should have dot1q capability.


  • Other Network Infrastructure Subjects
Hall of Fame Super Blue

Re: Encapsulation command in subif


From memory i believe you need IP PLUS at a minimum to support dot1q.


New Member

Re: Encapsulation command in subif

Hi Jon,

Thanks... how do I identify an IP plus IOS image file?


Re: Encapsulation command in subif

Jon is correct you are running only IPBASE code which does not support it , need at least ipplus code 12.2X or higher .

Re: Encapsulation command in subif

Hi Dan.

you're right as this document does.

But you need to make sure that by using the cisco navigator.

As far as I see you should use c2600-is-mz.122-4.T.bin IOS that is IP-PLUS feature set.Kindly check the ios you want for sure!

Edit : Jon and Glen are absolutely right. I didn't see your replies.

Hopes this helps


New Member

Re: Encapsulation command in subif

Also, keep in mind that typically trunking can't be configured on 10Mbps interfaces it needs to be at least a fastethernet interface.

New Member

Re: Encapsulation command in subif

Do you mean it wont let you configure it?

Or it will let you, but it just wont work?

Hall of Fame Super Blue

Re: Encapsulation command in subif


You can do 802.1q on a 10Mbps interface on a 2610 router with the right IOS. See attached link for more details.



New Member

Re: Encapsulation command in subif

Thanks for pointing that out. There are exceptions to everything...

Hall of Fame Super Bronze

Re: Encapsulation command in subif

As other indicated, you need IP Plus for dot1q but I'm afraid you won't be able to upgrade unless you upgrade your flash and memory.

8MB isn't enough for that image, you need 16MB flash and at least 48MB DRAM.