Ping process

Ping Process
Purpose : What happen to Cisco switch when ping is going

 

 

<pre-requsite>

1. New two PCs are connected to SW1

2. an each PC has IP.
PC1 : 10.1.1.1/24
PC2 : 10.1.1.2/24

3. SW1 has no configuration at all but just interfaces for PCs are ‘no shutdown’



<Process>
1. SW1 works for STP to the interfaces. it will take almost all 50 seconds.

2. On PC1, Ping is tried to PC2 (ex: ping 10.1.1.2)

3. PC1 sends ARP request to SW1
ARP request has source MAC, IP and destination IP but hasn't destination MAC.
ARP request is a broadcast so destination MAC is a broadcast MAC address.

 

 

4. SW1 adds PC1's MAC address and IP and interface to MAC address table and flood the ARP request to all the interface within same vlan.(there are just two interfaces here.)


5. PC2 sends ARP reply to PC1 after receiving ARP request and adding source MAC to the ARP reply packet (ARP reply is an unicast)

 

 

6. SW1 adds PC2's MAC address and IP and interface to MAC address table and forward the ARP reply to the interface connected to PC1 after looking up the mac address table.

 

 

7. PC1 receives PC2's ARP reply and sends ICMP request to PC2 by an unicast.

8. SW1 looks up the mac address table and sends ICMP request to a interface matched with destination IP of the packet

9. PC2 sends ICMP reply to PC1 after receiving ICMP request

10. SW1 looks up the mac address table and sends ICMP reply to a interface matched with destination IP of the packet

11. PC1 receives ICMP reply.