CCNA Question

Unanswered Question
Mar 12th, 2008

Hi all, When setting up a trunk between a switch (2950) port and router fast ethernet port , I configure the switchport to trunk, but on the router port (which I have configured using subinterfaces because of Vlans on the switch) I get this message: Configuring IP routing on a LAN subinterface is only allowed if that

subinterface is already configured as part of an IEEE 802.10, IEEE 802.1Q,

or ISL vLAN. Think I need some additional configuration on the router port, can anyone advise ?? The material Im reading doesnt give this information.

I have this problem too.
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mheusing Wed, 03/12/2008 - 04:56


Usually it is helpful for the community to post your router config to understand, what caused the issue.

The router config should look like this (numbers and IP addresses might be different):

interface FastEthernet1/0.1234

ip address

encapsulation dot1Q 100

The latter command matches the VLAN number in the switch. Note, for demonstration purposes I have used a subinterface number different to the VLAN ID, as the subinterface number is irrelevant for the trunking. Best practice, however, is to use the same subinterface number as the VLAN number, as this simplifies operations.

Hope this helps! Please use the rating system.

Regards, Martin


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