Jagdeep Gambhir Mon, 10/08/2007 - 05:02

Yes we can, here is an example

Router(config)#int s0/0

Router(config-if)#no shut

Router(config-if)#int s0/0.1 point-to-point

Router(config-subif)#ip add x.x.x.x



nambi_gct Mon, 10/08/2007 - 05:43

Hi Naidu,

These sub interfaces can be used in frame relay environment.You can create a point to point or point to multipoint sub interface to connect to your remote sites using FR.



Richard Burts Mon, 10/08/2007 - 05:57


To add a little to the explanation from Nambi: certain encapsulations like Frame Relay do support configuration of subinterfaces. But other serial encapsulations like PPP or HDLC do not support configuration of subinterfaces.

The main use of subinterfaces in Frame Relay is to be able to separate out various PVCs that are assigned over the serial link. If you have a Frame Relay connection over a serial interface you might have 4 PVCs from the provider on that link. Without subinterfaces all PVCs would operate on the physical interface in a multipoint mode. If you configure subinterfaces then you could create 4 separate point to point subinterfaces and assign a PVC to each subinterface which would operate in point to point mode rather than multipoint mode. There are sometimes advantages to operating in point to point mode such as the operation of split horizon.



ilnaiduccna Mon, 10/08/2007 - 21:04

Hi all,

Thanks to JG, Nambi and Rick for their good explaination.

As Rick told PPP or HDLC do not support on serial subinterfaces when using Frame Relay Technology then which encapsulation will do support for FR.



Richard Burts Tue, 10/09/2007 - 03:41


You can not do Frame Relay over an encapsulation like PPP or HDLC. Frame Relay is a separate encapsulation.



ilnaiduccna Tue, 10/09/2007 - 03:54

Hi Rick,

Apologize to my misread.

Yes I understand your prior post thanks a lot.



Mohamed Sobair Tue, 10/09/2007 - 04:39


Adding to Rick's comment that you can run PPP over Frame-relay for the purpose of Authentication since Frame-relay by default doesnt support features like (Authentication,Link Quality,Reliable transmission).

Running PPP over FR could enable these features.


Mohamed Sobair


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