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802.1Q or dot1Q encapsulation


I have a router with fastethernet interface. Current version 12.0(7)T, RELEASE SOFTWARE (fc2). Why I can't configure the dot1Q encap into this interface. Is it because the IOS not supported.

Cisco Employee

Re: 802.1Q or dot1Q encapsulation

Hey there

The version that you are running does indeed support Dot1Q trunking. You didn't specify which router, but the bottom line is that Dot1Q encapsulation is specified on the SUB-INTERFACES, not on the main interface. The main interface holds the IP for the Native VLAN. All the other VLANs need to be configured on the sub-interfaces of the physical port and it is there that the "encapsulation dot1q " command is required.

Here is a document on configuring Dot1Q trunking on 2600s running 12.0(x)T:

Basically, you will configure a subinterface for all the different VLANs.

I.e. If you had 4 VLANs (1, 2, 3,4) coming from a trunk on a switch.. you would configure 3 sub-interfaces for the 3 encapsulated VLANs, and then configure the main physical interface for the Native (non-encapsulated) VLAN. in this example, we'll assume that VLAN 1 is the native VLAN, so we'll assign its subnet to the main interface.

/* The physical interface corresponds to the native VLAN

int fast 0/0

ip address

/* The first sub-interface is for the first encapsulated VLAN, which is VLAN2 in

/* our scenario

int fast 0/0.2

ip address

encap dot1q 2

int fast 0/0.3

ip address

encap dot1q 3

int fast 0/0.4

ip address

encap dot1q 4

I hope that this helps,



Re: 802.1Q or dot1Q encapsulation

Not sure if this is true for all versions of IOS or for all Cisco routers, but at least some require the IOS feature set to be "Plus" in order to do sub-interfaces and dot1q encapsulation.

Community Member

Re: 802.1Q or dot1Q encapsulation


The router is cisco 7204VXR (NPE300) processor with 57344K/40960K bytes of memory. The poroblem is, when I creating the subinterface onto it, I didnt see any command encapsulataion ... as below

myrouter(config)#interface fa0/0.2


Interface configuration commands:

arp Set arp type (arpa, probe, snap) or timeout

backup Modify backup parameters

bandwidth Set bandwidth informational parameter

bgp-policy Apply policy propogated by bgp community string

carrier-delay Specify delay for interface transitions

cdp CDP interface subcommands

clns CLNS interface subcommands

default Set a command to its defaults

delay Specify interface throughput delay

description Interface specific description

exit Exit from interface configuration mode

ip Interface Internet Protocol config commands

isis IS-IS commands

iso-igrp ISO-IGRP interface subcommands

llc2 LLC2 Interface Subcommands

mls mls router sub/interface commands

mpls Configure MPLS interface parameters

mtu Set the interface Maximum Transmission Unit (MTU)

no Negate a command or set its defaults

ntp Configure NTP

rate-limit Rate Limit

Do the IOS (tm) 7200 Software (C7200-P-M), Version 12.0(7)T, RELEASE SOFTWARE (fc2) support 802.1Q or ISL ??

Cisco Employee

Re: 802.1Q or dot1Q encapsulation

You'll need IP Plus feature set(c7200-is-mz.120-7.T.bin). you have Service Provider feature set

Community Member

Re: 802.1Q or dot1Q encapsulation


In my understanding for IOS 12.0.7 to support encap on ethernet inter. require IP Plus feature set. We have a plan to upgrade for higher version 12.2.(11)T do this can support encap. dot1Q on the interface. ?

I have other 7200 router (7206VXR (NPE400) processor (revision A) with 245760K/16384K bytes of memory - c7200-p-mz.122-11.T1.bin) it does support encap. dot1Q. The IOS feature set still Service Provider feature set. My question is is IOS 12.2(11)T1 IP plus supported. ?

I'm still confused on IOS ver capability.. can somebody point me the url..

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