The fundamental differentiator between hubs and switches lies in their forwarding logic. While hubs operate as dumb repeaters (OSI Layer 1), switches make intelligent forwarding decisions by maintaining a MAC address table (Layer 2 operation). Here's the technical breakdown:

// Simplified switch forwarding logic pseudocode
void handlePacket(Packet p) {
    if (macTable.contains(p.destMAC)) {
        forwardToPort(macTable.get(p.destMAC));
    } else {
        floodToAllPortsExcept(p.ingressPort);
    }
    updateMacTable(p.srcMAC, p.ingressPort);
}

Every Ethernet switch maintains a dynamic mapping of MAC addresses to physical ports. Consider this real-world example from a Cisco switch:

Switch# show mac address-table
          Mac Address Table
-------------------------------------------
Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
 1      0050.7966.6800    DYNAMIC     Gi0/1
 1      00e0.4c3f.59a1    DYNAMIC     Gi0/2

While basic switches operate purely at Layer 2, multilayer switches (L3 switches) can perform IP routing. These maintain both:

• MAC address table (for Layer 2 switching)
• IP routing table (for Layer 3 routing)

// L3 switch forwarding logic
void routePacket(Packet p) {
    if (isLocalSubnet(p.destIP)) {
        // Layer 2 switching
        if (macTable.contains(arpCache.get(p.destIP))) {
            forwardToPort(macTable.get(arpCache.get(p.destIP)));
        } else {
            sendArpRequest(p.destIP);
            queuePacket(p);
        }
    } else {
        // Layer 3 routing
        RouteEntry route = routingTable.lookup(p.destIP);
        if (route != null) {
            rewriteHeaders(p);
            forwardToPort(route.nextHop);
        }
    }
}

The Layer 2 vs Layer 3 distinction affects these real-world scenarios:

When troubleshooting, these commands reveal the switching logic:

# Cisco IOS
show mac address-table dynamic
show arp
show ip route

# Linux bridge (software switching)
bridge fdb show
ip neigh show

You're absolutely correct about the fundamental difference between switches and hubs. A network switch operates at Layer 2 (Data Link Layer) of the OSI model and uses MAC addresses to make forwarding decisions. Here's how it works:

# Simplified switch forwarding logic (pseudocode)
def handle_packet(incoming_port, packet):
    src_mac = packet.source_mac
    dest_mac = packet.destination_mac
    
    # Learn source MAC and port mapping
    mac_table[src_mac] = incoming_port
    
    if dest_mac in mac_table:
        # Forward to specific port if MAC is known
        forward_to_port(mac_table[dest_mac], packet)
    else:
        # Flood to all ports except incoming (unknown unicast)
        flood_ports(packet, exclude=incoming_port)

Switches primarily work with MAC addresses, not IP addresses. Here's why:

• MAC addresses are hardware addresses burned into network interfaces
• IP addresses are logical addresses assigned by software
• Switches maintain a MAC address table (CAM table) mapping MACs to ports

Standard Layer 2 switches don't examine IP headers, but there are exceptions:

# Example of when a switch might inspect IP (Layer 3 switch)
class Layer3Switch(Switch):
    def handle_packet(self, port, packet):
        if is_ip_packet(packet):
            # Can make routing decisions based on IP
            if self.has_route(packet.dest_ip):
                next_hop = self.routing_table[packet.dest_ip]
                self.forward_to_mac(next_hop.mac, packet)
            else:
                super().handle_packet(port, packet)
        else:
            # Default to Layer 2 behavior
            super().handle_packet(port, packet)

Understanding this distinction helps with:

• Network troubleshooting (ARP issues vs. routing problems)
• VLAN configuration (Layer 2 segmentation)
• Security implementations (MAC filtering vs. IP filtering)

Here's how to view a switch's MAC address table on Cisco devices:

Switch# show mac address-table
          Mac Address Table
-------------------------------------------
Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
   1    0050.7966.6800    DYNAMIC     Fa0/1
   1    0050.7966.6801    DYNAMIC     Fa0/2