what is the purpose are using " IP VRF Forwarding " command, very confused to know about this command, whether it is necessary to use in core switch like supervisor engine 4500 series.please say the correct answer. FYI here i enclosed the running config which they are using that command.
ip vrf mgmtVrf
See here for the explaination of Fa1 and the mgmtVrf on the 4500 switch:
Effectively its just a physical out of band management port.
Some people use it, others don't.
I find the question a bit confusing. In the text of the question he seems to be asking about ip vrf forwarding but in the example he shows ip vrf mgmtVrf.
The response from devils advocate addresses the use in the example. In that case it would create one routing table associated with the management interface which does create what amounts to an out of band connection for management. If the question is really about ip vrf forwarding then that would create another vrf and its associated routing table which would be separate from the global routing table.
I wonder if he is referring to the fact that Fa1 is part of the mgmtVrf VRF as below:
interface FastEthernet1 ip vrf forwarding mgmtVrf