INTERVIEW QUESTIONS ON SWITCHING WITH ANSWERS

TOP INTERVIEW QUESTIONS ON SWITCHING

1. What happens when a frame is received on a switch port

The switch looks into the source mac-address of the frame and adds it to the mac-address table. It then looks into the mac-address table and forwards the frame to the appropriate destination.

2. What is the fundamental difference between switch and hub

A switch forwards all the frames only to the intended recipient, but hubs forward frames to all devices connected to it.

3. Which is the vendor neutral vlan standard

IEEE 802.1Q

4. Can two device belonging to same IP networks communicate if they are configured on different vlans

This is not possible, since intervlan communication would either need a L3 switch or a router.

4. Can ARP packets from one VLAN reach another VLAN

No. VLANS are used to segregate broadcast domains. ARP packets are broadcast packets and would not reach the other VLAN.

5. How is flooding and broadcasting different from a switching perspective.

A frame is flooded on a switch, when the destination mac-address in the frame is not available on the switch. The switch sends out the frame to all ports on the switch, excluding the port on which it was received. Broadcasting is used for frames which has the destination address FF-FF FF-FF-FF-FF. When such a frame is encountered, the frame is broadcasted to all ports on the switch, excluding the port on which it was received.

6. How many broadcast domains are there on a 24 port switch and a 24 port hub

A broadcast domain is the area on which a broadcast traffic from one device would be received by other devices. A switch and a hub contains one broadcast domain. Consider the following scenarios. When a PC is connected to a hub, and it sends broadcast traffic, the data is sent out to all ports on the hub. When the PC is connected to a switch and it sends broadcast traffic, it is also send to all ports on the switch. In hubs, irrespective of whether the traffic is broadcast or unicast, it is sent to all ports, because hubs don’t understand the type of traffic but just signals. On a switch, when a broadcast traffic is received (frame with mac-address value as FF-FF-FF-FF-FF-FF), it understands that the frame has to be broadcasted and would be sent to all ports.

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