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New Member

Routed port configured as native vlan

I have attached a diagram with this discussion. First please have a look at it.

The thing is; I had seen on design recently. There was more than 20 sub interfaces with IP address assigned in a router which was connected to

a switch. The port was obviously a trunk port as it was supposed to make a flow for more than 20 vlans. The confusion part for me is: there

was IP address in the actual physical interface too. I didn't understand why its there in the first place.

Would somebody share me the scoop??

 

Thank You in advance.

 

4 REPLIES
New Member

IP address set on the

IP address set on the physical interface will serve the native vlan of the trunk.

It is the same as if you configured another sub-interface and set native vlan on it.

 

Cisco Employee

Hi Ganesh.,To be frank I dont

Hi Ganesh.,

To be frank I dont see any reason to have the ip address on the main interface.  It is just like having native vlan concept.

Please find below testing:

Example:

 

I have router connecting to the Switch.

Router---F0/1--------------------F0/1---Switch

Router f0/1- ip address 50.0.0.1 /24---

f0/.1---ip address 10.0.0.2/24

f0/.2--ip address 20.0.0.2/24

f0/.3- ip address 30.0.0.3/24

 

Switch

F0/1--Switch port mode trunk----switch trunk encap dot1q --Switch trunk native vlan 50.>>> configuring native vlan as 50.

vlan 10--ip address 10.0.0.1/24

vlan 20---ip address 20.0.0.1/24

vlan 30 -ip address 30.0.0.1/24

vlan 50--ip address 50.0.0.2/24

 

Now you will have reachability to all the network. Were in Vlan 50 is your native vlan now.

 

HTH

Regards

Inayath.

New Member

Thank you for your response

Thank you for your response.

yes! the vlan associated with the physical interface has been configured as native vlan. So, I'm confused here why we made the physical interface a part of native vlan.

Please clarify me.

My question may seem like a query from a naive, sorry for that.

And thank you in advance


 

Cisco Employee

Ganesh,There are two ways to

Ganesh,

There are two ways to configure native parameter on the router:

1- To assign the ip address to the main interface.

2- To configure the folowing parameter under the subinterface to make the vlan to be part of native vlan:

 

example: Vlan 50 as native vlan:
conf t

interface FastEthernet 1/1.50
encapsulation dot1q 20 native

HTH

Inayath

*Plz rate all usefull posts.

 

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