Lecture on Networking: Switches, MAC Addresses, ARP, and PoE
Switches and MAC Address Tables
Role of a Switch: Forwards traffic based on the destination MAC address in an Ethernet frame.
Builds an active list of devices using inbound traffic and source MAC addresses.
Associates MAC addresses to specific physical interfaces.
Spanning Tree Protocol (STP): Ensures no loops occur on the switch network.
Traffic Forwarding Process:
Single Switch: When a device (Sam) sends traffic to another (SGC server), the switch uses its MAC address table to send traffic to the correct interface.
Multiple Switches: The same process occurs on each switch in the path, with each switch using its own MAC address table to forward traffic.
Building MAC Address Table:
Switch examines source MAC address of incoming traffic and associates it with the receiving interface.
Upon initial power-up, the switch floods unknown destination MAC traffic to all interfaces until it learns the addresses.
Address Resolution Protocol (ARP)
Purpose: Obtains MAC addresses of remote devices using the device's IP address.
Process:
Device queries the network for a specific IP address.
The target IP address responds with its MAC address.
ARP Cache: Local computer keeps a cache of known MAC addresses, which can be viewed using arp -a.
Example:
Ping a device to initiate an ARP request and update the ARP cache.
Use packet analyzers like Wireshark to capture and analyze ARP communication.
IPv6 and Neighbor Discovery Protocol (NDP)
Difference from IPv4: IPv6 does not use broadcasts; it uses multicast for address resolution.
Neighbor Discovery Protocol (NDP):
Replaces ARP in IPv6.
Uses ICMPv6 for neighbor solicitation (NS) and neighbor advertisement (NA) messages.
Supports Stateless Address Autoconfiguration (SLAAC) and Duplicate Address Detection (DAD).
Power over Ethernet (PoE)
Function: Sends power along with data over Ethernet cables to power devices like access points and VOIP phones.
Methods:
Endspan: Power from the switch.
Midspan: Power from an injector.
Modes:
Mode B: Uses spare pairs in 10/100 Mbps networks.
Mode A: Uses the same wires for power and data in gigabit networks.
Standards:
IEEE 802.3af (2003): Original PoE standard, 15.4W power, 350mA current.