Need to get some understanding on L2 l L3 Vlan

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May 11th, 2008
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Hi Friends,


I have a doubt, if it seems very simple question plz forgive: )


I have a LAN setup with few cisco 3750 switches, where i am using VTP mode as Transparent.


What will happend If i create a L3 Vlan SVI interface with out creating L2 on the switch.


What is the difference in creating L3 Vlan with L2 and with out L2 ?


Please can any one take some effort to brief me about this..


Thanks a lot


Regards


Jacob

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JORGE RODRIGUEZ Sun, 05/11/2008 - 14:45
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Jacob,


When you create an SVI interface because is a virtual interface without any physical associations, at least you must have one L2 VLAN created for it with a connected device or host on a switchport to associate it with that newly created SVI interface in order for the SVI interface to be fully up and functional. A virtual SVI interface without any L2 vlan association in a switchport will just be an idle SVI interface, this would be the case when no L2 VLAN is associated with L3 interface the expected output of " show ip interface brief " for the SVI will be Up/Down.



What is the difference in creating L3 Vlan with L2 and with out L2 ?


Same as above answer, once you create L2 VLAN in vlan database and connect a device or host on a switchport that will bellong to L3 SVI network that you have created, the SVI interface will be a fully functional as well as fully routable and be able to route between any other L3 interfaces or SVI you have similarly created.



HTH

-Jorge


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