Regarding sub interface

[ncnaveen_arasu]

                   Hi Friends,

When do we assign the ip for the Physical interface as well as the sub interface of the same physical interface. and enable the routing protocols on both physical and sub interface. Is there any significance for using this kind of setup.

Please clarify.

Thanks in advance.

Naveen

[John Blakley]

The implementation is going to dictate what it's used for, but the physical interface defaults to native vlan 1. Anything underneath would be tagged. You can't change the encapsulation method on the primary interface, but on subinterface you have to configure "encapsulation dot1q " in order to support tagging.

HTH,
John

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[gaurav bhardwaj]

when you want to comunicate different network by a single port then you will provide IP to subinterface. like vlan configuration you have three vlan then you will make 3 subinterface then give ip to that subinterface.

[ncnaveen_arasu]

HI thanks for the reply,

If we apply an IP for physical interface for one network and create a sub interface under that same physical interface and assign diffrent network IP will it work.

[kcnajaf]

Hi Naveen,

This will work. But please be aware that you will not be able to change the encapsulation the the physical interface and you will have to use "encapsulation dot1q " on the subinterface in order to support tagging like John mentioned in previous post.

These points are applicable only for enthernet interface and if you are on serial interface you dont have to mention the encapsultion on subinterface and with out specifying the encapsulation communication will happen.

Hope that helps.

Regards

Najaf

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