Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

Vlan problem

i have a router 7200 connected(g0/2) with switch 3550(g0/12). I have on my switch 3 vlans. So i did the following:

1. The interface of switch(g0/12) to trunk mode encapsulation dot1q

2. I create 3 subinterfaces (g0/2.1, g0/2.2,g0/2.3)on the router with dot1q encapsulation with different networks.

3. i removed the ip address of the interface(g0/2) of the router and i put ip addresses on subinterfaces.

i do not know what i am doing wrong but i seems it does not work. Did i forget anything? Did i did something wrong?

Meantime the interface of the router(g0/2) (not subinterfaces) i saw that it was encapsulation dot1q vlan id 1 . The others interfaces(g0/1 etc) of the router which i did not create subinterfaces were encapsulation ARPA.

i tried to change that but the int(g0/2) does not accept encapsulation.




Re: Vlan problem


can you post the output of show run and show interface g0/2.x ?



Re: Vlan problem

It should work ok in theory. Please post configurations of gi0/2 and it's subinterfaces from 7206, and configuration of gi0/12 on your 3550.

New Member

Re: Vlan problem


have you forget to say that the intg0/2 is now an Switchport ?

router: int g0/2


switchport trunk

switchport trunk allowed vlan xy


New Member

Re: Vlan problem

you shouldn't give any commands on Physical interface,you should use sub interfaces like exmple vlan int g0/2.1

vlan int g0/2.2

New Member

Re: Vlan problem

I restart the router and configured the router again . Now it seems to work . I did encapsulation only on subinterfaces not at the interface. Is that enough? And also here the result of show int g0/2 which I did not do encapsulation and also remove the ip address:

GigabitEthernet0/2 is up, line protocol is up

Hardware is BCM1250 Internal MAC, address is 000f.2417.ab1a ?

MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation 802.1Q Virtual LAN, Vlan ID 1., loopback not set

Keepalive set (10 sec)


Why it shows the :

Encapsulation 802.1Q Virtual LAN, Vlan ID 1., loopback not set



Hall of Fame Super Silver

Re: Vlan problem


When you configure the physical interface with subinterfaces then the IOS knows that the interface is trunking and that the encapsulation must be 802.1Q. In 802.1Q the native VLAN is sent untagged and by default the native VLAN is VLAN 1. So this message is reflecting the default behaviors.



CreatePlease to create content