Routed port configured as native vlan

[ganeshdhungana]

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.

[Petar Loncarec]

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.

[InayathUlla Sharieff]

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.

[ganeshdhungana]

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

[InayathUlla Sharieff]

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

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