4 PCs and 3 bridges are connected as shown below. Assume all the ARP caches are

Question

4 PCs and 3 bridges are connected as shown below. Assume all the ARP caches are up to date and all the forwarding tables are empty. Host1 sent 10 ping request packets to Host2. (Host1% ping –c 10 IP_Host2).

Answer the following questions:

a. After the 10 successful pings, list all the entries in the forwarding table of each bridge.

b. How many ICMP echo request/reply packets did Host3 and Host4 observe?

Bridge Etho Bridge Bridge1 Eth1 Bridge1 Etho Bridgelaridge2Ethi Bridge2 Etho Bridge Eth1 Bridge3 IPO Bridge 1 IPO Bridge IP1 Bridge2 IPO Bridge3 Ethernet Eth me Ethe net Ethernet Eth Host1 Eth Host 2 Eth Host 3 Eth Host Host IP Host1 IP Host IP Host4 Host1 Host2 Host 4

Explanation / Answer

a) Initially since, host1 does not who the host2 is it will multicast to all the posts and get the echo requests back, so all the addresses will be known from host1, but not from others , hence the table will be the following:

Because, these will be the default settings for bridge1 as it will the one being used for 10 pings.

b)Since, after the first request the host3 and host4 will send the echo packets and after that host1 will not send the packets after that. Hence host3 and host4 will get only 2 ICMP packets.

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