Ethernet LAN Switching

Authors
  • avatar
    Name
    Michael Bui
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Overview

In this lab we're going to examine traffic going through switches. The switches will start with empty MAC address tables & empty ARP tables.

This is the lab layout:

Instructions

PC1 pings PC3. What messages will be sent over the network & which devices will receive them?

Ping PC3 192.168.1.3 from PC1

ARP Process

  1. PC1 sends an ICMP message to 192.168.1.3
  2. PC1 does not know the MAC address of PC3 so ARP is constructed for PC3's IP address
  3. SW1 adds PC1 to MAC address table -> SW1 broadcasts the ARP request out all ports except source
  4. PC2 processes frame and drops it because it's not for the destination IP
  5. SW2 adds PC1 to MAC address table -> SW2 broadcasts request out all ports except source
  6. PC4 drops
  7. PC3 updates it's ARP table -> PC3 sends out a reply with MAC address
  8. Frame is sent to SW2 -> SW1 -> PC1
  9. PC1 updates it's ARP table

Ping Process

  1. PC1 sends out ICMP echo request
  2. PC1 has the MAC address of PC3 from ARP table so it sets a destination MAC address and sends it out
  3. SW1 receives frame -> SW1 sees that it has destination MAC address in it's MAC table and sends it out port G0/1
  4. SW2 receives frame -> SW2 sees that it has destination MAC address in it's MAC table and sends it out port F0/1
  5. PC3 receives frame -> decapsulates PDU from frame -> decapsulates packet because it was destined for this IP
  6. PC3 processes the ICMP packet & sends an echo reply to the IP address of PC1
  7. Frame is sent to SW2 -> SW1 -> PC1
  8. PC1 decapsulates packet & receives the echo reply message