The following are some ARP interview questions

1. Is ARP request packet unicast, multicast or broadcast ?

ARP request is a broadcast packet.

2. Does ARP packets use IP header

ARP does not use IP header. It is a layer 2 protocol.

3. Can routers process ARP packets

Yes, Routers can process Layer 2 and Layer 3 Packets.

4. Which field in an ARP request header is blank / Null

The target mac-address value is blank as the use of ARP request is to find the target mac-address.

5. Does ARP requests in one VLAN reach another VLAN

No. ARP request packets are broadcast. As VLAN’s segregate broadcast packets, broadcast packets from one VLAN does not reach another vlan.

6. Is ARP packets initiated by the user or the operating system

The operating system internally initiates ARP packets.

7. Can ARP packets be used to find the mac-address of systems residing on different networks.

No. ARP packets are layer 2 packets. They can be used only within a network.

8. Does ARP reply packets contain IP address fields ?

Yes they contain the sender and target IP address fields.

9. What does a switch do when it receives a ARP request packet.

It looks into the source mac-address value in the frame, adds it to its mac-address table and broadcasts the ARP packet to all other ports as the packet is a broadcast packet.