Students to Discuss Solution: ARP (Week 9)

Nodes 1, 2, 3 and 4 on an Ethernet LAN have Ethernet addresses E1, E2, E3 and E4, and IP addresses I1, I2, I3 and I4, respectively. Assume that the nodes are connected via a star topology via a central Ethernet switch (typical star topology as shown in the lecture slides) All nodes maintain an ARP cache and respond to ARP queries immediately. Unless refreshed, ARP cache entries are timed out and removed if more than 15 minutes old. At time t = 0, assume that all the ARP caches are empty. After ARP responses are received subsequent to each of the following ARP queries, state which nodes have an Ethernet-IP address mapping for which other nodes in their ARP caches.

1. At time t = 5 minutes, node 1 broadcasts an ARP query for IP address I3, and node 2 broadcasts an ARP query for IP address I1.
2. At time t = 15 minutes, node 3 broadcasts an ARP query for IP address I2.
3. At time t = 25 minutes, node 4 broadcasts an ARP query for IP address I2.