Week 13 - Switching and VLANS.pptx
Transcript
Week 13: Switching and VLANs NTWK8021 – Network Planning What we covered last lecture • CLI Structure • Device Commands • Static and Dynamic Routing Protocols Q/A Any Questions? Welcome to Week 13! This week, we are going to cover Switching and VLANs After this lecture, you should be able to...
Week 13: Switching and VLANs NTWK8021 – Network Planning What we covered last lecture • CLI Structure • Device Commands • Static and Dynamic Routing Protocols Q/A Any Questions? Welcome to Week 13! This week, we are going to cover Switching and VLANs After this lecture, you should be able to… • • • • Understand Layer 2 Switching and how it works Understand VLANs including access ports and trunk ports Understand VLAN tagging Understand commands for setting up VLANs Part 1: Switching NTWK8021 – Network Planning Introduction to Switching and Review • A network switch is a device that connects devices within a local area network (LAN) • Key Points – Operates at Layer 2 (Data Link Layer) of the OSI model – Manages traffic based on MAC addresses – Reduces collision domains • Review – How do switches reduce Collision Domains? Switched Network Design • • • • A typical, contemporary, and complete switched network design/implementation would look something like this. There is a router implemented. The router creates and handles logical segmentation. What makes Layer 2 switching so efficient is that no modification to the data packet takes place. Switching Functions at Layer 2 • There are three main functions of Layer 2 switching – MAC Address learning – Forward/filter decisions – Loop avoidance MAC Address Learning Host A Host B Host C Host D Forwarding/Filter Table When the hosts start communicating, the switch places the source hardware address of each frame in the table along with the corresponding port Forwarding/Filter Table Evaluation Loop Avoidance • In redundant network designs, loops can cause issues. STP (Spanning Tree Protocol) is a protocol that helps prevent loops by creating a loop-free logical topology • More details on STP will be provided in NTWK8031 Switching Loop Example • • If you have more than one path to a destination, switching loops can occur STP was developed to prevent loops from happening Part 2: VLANs NTWK8021 – Network Planning What is a VLAN? • VLAN stands for Virtual Local Area Network • How VLANs work: – Logical Segmentation – Each VLAN operates as its own broadcast domain – Identification using VLAN IDs (1-4095) VLAN Diagram Benefits of VLANs • Enhanced Network Security – VLANs can be isolated – Can restrict access by VLAN – An example is to prevent everyday users from accessing essential Databases • Scalability: – It’s easy to add or remove VLANs as needed • Improved Network Performance. – Smaller Broadcast Domains Layer 2 Switch Limitations • Inter-VLAN Routing: – On a Layer 2 switch, VLANs are separate broadcast domains – To allow communication between VLANs, a Layer 3 device, like a router or Layer 3 switch, is needed Configuring VLANs on a Layer 2 Switch • Setting up VLANs on a Layer 2 switch is a three-step process Step 1: Creating the VLAN Step 2: Assigning interfaces as Access Ports Step 3: Assigning interfaces as Trunk Ports Access Ports vs Trunk Ports • Access Ports – Belong to a VLAN and do not tag the outgoing frames. They're used to connect end devices like PCs and printers • Trunk Ports – They can carry frames for multiple VLANs and tag frames with the appropriate VLAN ID. They're used to connect switches to each other VLAN Tagging and 802.1Q • VLAN Tag – When frames traverse a trunk link, a tag is added to the Ethernet frame, denoting its VLAN ID. This helps switches identify which VLAN a frame belongs to and forward it accordingly • 802.1Q Protocol – An IEEE standard that supports VLAN tagging on Ethernet networks. It's responsible for adding a tag to the original frame when it goes out on a trunk link and removing the tag when it enters an access link 802.1Q Encapsulation Best Practices for VLANS • Reserve a few VLAN IDs for future use • Set descriptive names for VLANs • Isolate all unused ports and put them in an unused VLAN • Always set a native VLAN that's different from user VLANs Part 3: VLAN Commands NTWK8021 – Network Planning VLAN Commands • The next set of slides will go through setting up a VLAN, setting access ports, setting up trunk ports and commands that can be used to verify configuration Creating VLAN Example Switch(config)#vlan 2 Switch(config-vlan)#name Sales Access Port Example Switch(config)#interface range fa0/1 – fa0/8 (Selects fa0/1 – fa0/8 to configure) Switch(config-if-range)#switchport access vlan 2 (Identifies that fa0/1 – fa0/8 are access ports on VLAN 2) Viewing VLANs and Access Ports Trunk Port Example Switch(config)#interface fa0/24 Switch(config-if)#switchport mode trunk (Sets the port to be a trunk port) Switch(config-if)#switchport trunk allowed vlan 2 (Allows vlan 2 tags through the trunk) Viewing Trunk Ports Switch# show interfaces trunk Port Fa0/24 Mode on Port Fa0/24 Vlans allowed on trunk 2 [output cut] Encapsulation 802.1q Status trunking Native vlan 1 VLAN Demonstration • We will now go through a demonstration on setting up VLANs • This demo will help prepare you for Practical Lab 5 next week To Be Continued • In your next course NTWK8031 you will be covering VLANs in more detail including – Inter-vlan Routing – Layer 3 Switching Q/A – End of Lecture Any Questions?
