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Basic Network Fundamental ( Change bridge priority without change VLAN ID, Root Bridge, Root port election, Root cost measurement)

How to change the bridge priority without change the VLAN ID? If you want to change the switch’s bridge priority you can only change the total bridge priority (bridge priority + extended system ID) in units of 4096. The STP bridge priority can only be changed in units of 4096. The valid values you can configure are: 0, 4096, 8192, 12288, 16384, 20480, 24576, 28762, 32768, 36864, 40960, 45056, 49152, 53248, 57344 or 61440. The extended system ID will then be added to this number to make the total bridge priority value. Why 32768 default bridge priority? It’s because this field is 16 bits in length, and the most significant bit is set 1 by default. Therefore, the default bridge priority was 32768 With the addition of the extended-system ID, adding the VLAN ID number to the bridge priority, that changed. So, the default VLAN ID is 1, therefore the bridge priority in total isn’t 32768, its 32769. In the default VLAN of 1, the default bridge priority is 32769, which is 32768+1. What is the...
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Basic Network Fundamental (BPDU (Bridge Protocol Data Unit) priciple, Bridge ID, Bridge Priority Calculation, Pre-Vlan Spanning Tree)

What exactly are these BPDUs used for? • Bridge Protocol Data Units (BPDUs) are the messages that are transmitted across LAN networks to enable switches to participate in Spanning Tree Protocol (STP) by gathering information about each other. • It contains information regarding switch ports such as port ID, port priority, port cost, and MAC addresses. • A switch sends BPDUs from their origin port to a multicast address with a destination MAC address. • Switches use one field in the STP BPDU, the Bridge ID field, to elect a root bridge for the network. • The switch with the lowest Bridge ID becomes the root bridge. • All ports on the root bridge are put in a forwarding state. What is the Bridge ID field? • There is a bridge priority field, which is 16 bits in length, and then there is the MAC address of the switch, which is 48 bits in length. • The default bridge priority is 32768 on all switches, so by default the MAC address is used as the tie-breaker (lowest MAC address becomes th...
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Basic Network Fundamental (Broadcast Strom, MAC Address Flapping, Spanning Tree Protocol (STP), STP Working principle, Details of Bridge Protocol Data Units - BPDU)

What is the Broadcast Storm? • The network will be too congested for legitimate traffic to use the network. This is called a Broadcast Storm. What is the MAC Address Flapping? • When frames with the same source MAC address repeatedly arrive on different interfaces, the switch is continuously updating the interface in its MAC address table. This called MAC address Flapping. What is the STP (Spanning Tree Protocol)? • STP stands for Spanning Tree Protocol (IEEE 802.1D) and it is a Layer 2 Protocol. • It prevents Layer 2 loops (broadcast storm and MAC address flapping) by placing redundant ports in a blocking state, essentially disabling the interface. • Interfaces in a forwarding state behave normally. They send and receive all normal traffic. • Interfaces in a blocking state only send or receive STP message, this is called BPDUs = Bridge Protocol Data units. How STP (Spanning Tree Protocol) works? • By selecting which ports are forwarding and which ports are blocking, STP creates a sing...
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Basic Network Fundamental (Virtual Trunking Protocol (VTP) Usage, Modes, Revision Number, Details of Server Mode, Transparent Mode, Client Mode)

  What is the VTP? • VTP allows you to configure VLANs on a central VTP server switch, and other switches (VTP clients) will synchronize their VLAN database to the server. • It is designed for large networks with many VLANs, so that you don’t have to configure each VLAN on every single switch. Cisco switches operate in VTP server mode by default. What is the VTP Versions? • There are three versions of VTP 1, 2 and 3. cisco modern switches support all 3 versions. • Version 1 – It supports VLANs 1 to 1001, and it does not recognize or propagate information about extended range 1006 – 4094 and it’s provided Lacks support for Token Rings VLANs or advanced features. • Version 2 – It provides same functionality as Version 1 and its support for Token Rings VLANs. Transparent mode switches can forward VTP advertisement in version 2. • Version 3 – It supports extended vlan range (1006 – 4094). It’s had primary and secondary VTP servers. What are the VTP Mode’s available? • There are three V...
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Basic Network Fundamental (Broadcast Strom, MAC Address Flapping, Spanning Tree Protocol, BPDU,)

What is the Broadcast Storm? ·         The network will be too congested for legitimate traffic to use the network. This is called a Broadcast Storm .   What is the MAC Address Flapping? ·         When frames with the same source MAC address repeatedly arrive on different interfaces, the switch is continuously updating the interface in its MAC address table. This called MAC address Flapping. What is the STP (Spanning Tree Protocol)? ·          S TP stands for Spanning Tree Protocol (IEEE 802.1D) and it is a Layer 2 Protocol. ·         It prevents Layer 2 loops (broadcast storm and MAC address flapping) by placing redundant ports in a blocking state, essentially disabling the interface. ·         Interfaces in a forwarding state behave normally. They send and receive all normal traffic. ·   ...
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Basic Network Fundamental (Multilayer or Layer 3 Switch and Usage of Layer 3 switch instead of Router, Switch Virtual Interfaces)

What is the Multilayer or Layer 3 switch? • A multilayer switch is capable of both Switching and Routing. It is Layer 3 aware. • A regular layer 2 switch is not layer 3 aware, it doesn’t think at all about IP addresses, it only cares about Layer 2 information like MAC addresses. • You can assign IP addresses to its interfaces, like a router. And you can configure routed ports which function like an interface on a router. • You can create virtual interfaces for the each VLAN and assign IP addresses to those interfaces. Why we use Multilayer or Layer 3 switch instead of router? • It can be used for inter-VLAN routing. • Inter-VLAN routing, it is using one connection for each VLAN between the router and switch. • But if you have many VLANs you probably won’t’ have enough interfaces on your router. • The router on a stick, which uses a single trunk connection which carries traffic from all VLANs between the switch and router for inter-VLAN routing. • This is efficient in terms of the numbe...
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Basic Network Fundamental (VLAN, Broadcast Domain, Benefits of using the VLAN, Inter Vlan Routing Detail)

What is the VLAN? • VLAN is partitioned and isolated broadcast domain into separate LAN network at Layer 2 (Data Link Layer). • The switch will consider each VLAN as a separate LAN and it will not forward traffic between VLAN’s. What is the Broadcast Domain? • LAN is a group of devices (PCs, Servers, routers, switches, etc.) in a single location (home, office, etc.) • A LAN is a single broadcast domain, including all devices in that broadcast domain. What is the benefit to using the VLAN? • When it comes to Performance - lots of unnecessary broadcast traffic can reduce network performance. • Whether it’s a broadcast from one end host or a switch that doesn’t know how to reach the destination MAC address, so it floods the frame, we should minimize unnecessary traffic in our network. • When it comes to Security – Even within the same office, you want to limit who has access to what. You can apply security policies on a router/firewall. • Because this is one LAN, PCs can reach each other ...
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Basic Network Fundamental (Network Switch Working principle, Half Duplex & Full Duplex, Difference between Switch vs Router)

  How Network Switch Work • When a device send frame to another device via switch, switch will receive the frame and check the source mac address availability in MAC Address table. • If it’s not available, then it will add the source MAC address into switch MAC address table. • Then switch check the destination device MAC address in the MAC address table, if its not available then the switch will flood the frame into all interfaces except source device connected interface. It’s called unknown unicast frame. • Once Frame reach the destination device, then destination device will reply to the switch. • Then switch will add the destination device MAC address into switch MAC Address table. • Then switch will forward the reply frame into source device interface, it’s called known unicast frame. Different between Switch and Router • Switches keep a MAC address table with their known destination MAC addresses and routers keep a routing table with their known destination networks. • Swit...
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