A network engineer is trying to deploy a PC on a network. The engineer observes that when the PC is connected to the network, it takes 30 to 60 seconds for the
PC to see any activity on the network interface card. Which Layer 2 enhancement can be used to eliminate this delay?

A. Configure port duplex and speed to auto negotiation.

B. Configure port to duplex full and speed 1000.

C. Configure spanning-tree portfast.

D. Configure no switchport.








 

Suggested Answer: C

When first powered on, each port goes through 4 states to ensure that there are no physical loops in the layer 2 broadcast domain. These steps are outlined as follows. With the initial version of spanning tree, this process could take from 30-60 seconds.
1.Blocking  A port that would cause a switching loop, no user data is sent or received but it may go into forwarding mode if the other links in use were to fail and the spanning tree algorithm determines the port may transition to the forwarding state. BPDU data is still received in blocking state.
2.Listening  The switch processes BPDUs and awaits possible new information that would cause it to return to the blocking state.
3.Learning  While the port does not yet forward frames (packets) it does learn source addresses from frames received and adds them to the filtering database
(switching database)
4.Forwarding  A port receiving and sending data, normal operation. STP still monitors incoming BPDUs that would indicate it should return to the blocking state to prevent a loop.
STP PortFast causes a Layer 2 LAN interface configured as an access port to enter the forwarding state immediately, bypassing the listening and learning states.
Reference: http://net.cmed.us/Home/ethernet-and-ip/spanning-tree-protocol

This question is in 300-115 Implementing Cisco IP Switched Networks (SWITCH) Exam
For getting Cisco Certified Network Professional (CCNP) Routing and Switching Certificate





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