08-31-2014 09:47 AM - edited 03-07-2019 08:35 PM
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.
08-31-2014 11:36 AM
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.
08-31-2014 11:51 AM
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.
08-31-2014 02:11 PM
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
08-31-2014 10:17 PM
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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