Solved: Vertual Interface on Router work on which OSI Layer

kirankumar.chamakura · ‎07-15-2008

when we make subinterfaces on Router Example(fa0/0.1) this subinterface work on which OSI Layer.

Richard Burts · ‎07-16-2008

To go back to Kiran's original question about which OSI layers works on virutal interfaces, a virtual interface such as an Ethernet subinterface works at all the same OSI layers that a physical interface works at.

So certainly it works at layers 2 and 3 as already mentioned. And to the extent that it might be the source or destination of TCP based traffic such as telnet we could say that it works at layer 4. And to the extent that it might be the source or destination of things like SNMP we might say that it works at all the way up to the application layer.

HTH

Rick

HTH

Rick

View solution in original post

sanjaynadarajah · ‎07-15-2008

Since the sub-interface has IPs on it, then it would be Layer 3.

HTH,

- sn -

mohammedmahmoud · ‎07-15-2008

Hi,

Well, to configure an Ethernet subinterface with an ip address (Layer 3) you must configure dot1q encapsulation with the appropriate VLAN first, and if you wish to do bridging (Layer 2) then you'll have to play with IRB (Integrated Routing and Bridging) or CRB (Concurrent Routing and Bridging) - since by default the router is capable of routing only (when ip routing is enabled, which is the default).

Router(config)#interface f1/3.1

Router(config-subif)#ip address 10.10.10.3 255.255.255.0

% Configuring IP routing on a LAN subinterface is only allowed if that

subinterface is already configured as part of an IEEE 802.10, IEEE 802.1Q,

or ISL vLAN.

Router(config-subif)#encapsulation dot1Q ?

<1-4094> IEEE 802.1Q VLAN ID

Router(config-subif)#encapsulation dot1Q 3

Router(config-subif)#ip address 10.10.10.3 255.255.255.0

BR,

Mohammed Mahmoud.

Richard Burts · ‎07-16-2008

To go back to Kiran's original question about which OSI layers works on virutal interfaces, a virtual interface such as an Ethernet subinterface works at all the same OSI layers that a physical interface works at.

So certainly it works at layers 2 and 3 as already mentioned. And to the extent that it might be the source or destination of TCP based traffic such as telnet we could say that it works at layer 4. And to the extent that it might be the source or destination of things like SNMP we might say that it works at all the way up to the application layer.

HTH

Rick

HTH

Rick

Richard Burts · ‎07-16-2008

Kiran

I am glad that my response helped to resolve your question. Thank you for using the rating system to indicate that your question was resolved (and thanks for the rating). It makes the forum more useful when people can read a question and can know that a response did help to resolve the question.

The forum is an excellent place to learn Cisco networking. I enourage you to continue your participation in the forum.

HTH

Rick

HTH

Rick