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2566897246 |
@@ -25,3 +25,7 @@ tags:
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[[Subnetting (Part 1)]]
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[[Subnetting (Part 1)]]
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[[Subnetting (Part 2)]]
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[[Subnetting (Part 2)]]
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[[Subnetting (Part 3 - VLSM)]]
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[[Subnetting (Part 3 - VLSM)]]
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[[VLAN (Part 1)]]
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[[VLAN (Part 2)]]
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[[VLAN (Part 3)]]
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[[DTP - VTP]]
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85
16. VLAN (Part 1).md
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85
16. VLAN (Part 1).md
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---
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id: 16. VLAN (Part 1)
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aliases: []
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tags: []
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---
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# VLAN (Part 1)
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## What is a [[LAN]]?
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Previously i said that a LAN is a group of devices (PCs, servers, routers, switches) in a single
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location (home office, etc.)
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A more specific definition: A LAN is a single [[broadcast domain]], including all devices in that
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broadcast domain.
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## Broadcast domains
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A broadcast domain is the group of devices which will receive a broadcast frame (destination [[MAC]]
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FFFF.FFFF.FFFF) sent by any one of the members.
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Perfomance: lots of unnecessary broadcast traffic can reduce network performance
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Security : Even within the same office you want to limit who has access to what. You can apply
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security policies on a [[router]]/[[firewall]]
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Because this is one LAN, PCs can reach each other directly, without traffic passing through the router
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So even if you configure security policies, they won't have any effect.
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Although we separated the three departments into three subnets ([[OSI|Layer 3]]), they are still in
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the same broadcast domain ([[OSI|Layer 2]])
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## What is a [[VLAN]]
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A [[switch]] will not forward traffic between VLANs, including broadcast/unknown unicast traffic
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- VLANs are configured on switches on a **per-interface** basis.
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- logically separate end hosts at Layer 2.
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The switch does not perform inter-Vlan routing. It must send the traffic through the router
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### VLAN configuration
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to display all the VLAN's available you can do the command
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```Cisco
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SW1#show vlan brief
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```
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By default all interfaces are set to VLAN 1
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But VLANs1, 10002-1005 exist by default and *cannot be deleted*
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to assign interfaces to a VLAN
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```Cisco
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SW1(config)#interface range g1/0 - 3
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SW1(config)#switchport mode access
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SW1(config)#switchport access vlan 10
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% Access VLAN does not exist. Creating vlan 10
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```
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An access port is a switchport which belongs to asingle VLAN, and usually connects to end hosts
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like PCs
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Switchports which carry multiple VLANs are called 'trunk ports' (More information on trunks in
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the next lesson)
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You can change the name of the VLAN with the command :
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```Cisco
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SW1(config)#vlan 10
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SW1(config-vlan)#name ENGINEERING
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```
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This Commang creates a VLAN.
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(In this case it was already automatically created when we assigned the interfaces)
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## Review
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- What is a (LAN)?
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- Broadcast domains
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- What is a Vlan
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- What is the purpose of VLANs?
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- How to configure VLANs on Cisco switches
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199
17. VLAN (Part 2).md
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199
17. VLAN (Part 2).md
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---
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id: 17. VLAN (Part 2)
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aliases: []
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tags: []
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---
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# VLAN (Part 2)
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## Trunk ports
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In a small network with few [[VLAN]]s it is possible to use separate interface for each VLAN
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when connecting switches to switches, and switches to routers.
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However, when the number of VLANs increases, this is not viable. it will result in wasted interfaces,
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and often routers won't have enough interfaces for each VLAN.
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You can use trunk ports to carry traffic from multiple VLANs over a single interface.
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Switches wil 'tag' all frames that they send over a trunk link.
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This allows the receiving switch to know which VLAN the frame belong to.
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Trunk ports = 'tagged' ports
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Access ports = 'untagged' ports
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### VLAN Tagging
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- There are two main trunking protocols: [[ISL]] (Inter-Switch Link) and [[IEEE 802.1Q]] (dot1q)
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- ISL is an old Cisco proprietary protocol created before the industry standard IEEE 802.1Q
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- IEEE 802.1Q is an industry standard protocol created by the [[IEEE]] (Institure of Electrical and
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Electronics Engineers)
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- You will probably NEVER use ISL in the real world. Even modern Cisco equipment doesn't support it
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For the CCNA you only need to learn 802.1Q
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#### inside Ethernet Header
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Preamble | SFF | Destination | Source | 802.1Q | Type
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The 802.1Q tag is inserted between the Source and Type/Length fields of the Ethernet frame.
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The tag is 4 bytes (32 bits) in length.
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The tag consists of two main fields:
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- Tag Protocol Identifier [[TPID]]
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- Tag Control Information [[TCI]]
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The TCI consists of three sub-fields.
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802.1Q tag Format
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+-----------------------------------+
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|16 bits | 3 | 1 |12 bits |
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| | bits | bit | |
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| TPID | TCI |
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| | PCP | DEI | VID |
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+-----------------------------------+
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##### TPID ( Tag Protocol Identifier)
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- 16 bits (2bytes) in length
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- Always set to a alue of 0x8100. This indicate that the frame is 802.1Q-tagged.
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##### PCP (Priority code point)
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- 3 bits in length
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- Used for Class of Service (CoS), which prioritizes iimportant traffic in congested network
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##### DEI ( Drop Eligible Indicator)
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- 1 bit in length
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- Used to indicate frames that can be dropped if the network is congested.
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##### VID (VLAN ID)
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- 12 bits in lenght
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- Indentifies the VLAN the frame elongs to.
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- 12 bits in length = 4096 total VLANs (2^12), range of 0 - 4095
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- VLANs 0 and 4095 are reserved and can't be used
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- Therefore the actula range of VLANs is 1-4094
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- Cisco's proprietary ISL also has a VLAN range of 1 - 4094
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more info https://en.wikipedia.org/wiki/IEEE_802.1Q
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## VLAN Ranges
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- The range of VLANs (1-4094) is divided into two sections:
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Normal VLANs: 1-1005
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Extended VLANs : 1006-4094
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- Some older devices cannot use the extended VLAN range, however it's safe to expect that modern
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switches will support the extended VLAN range.
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## Native VLAN
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- 802.1Q has a feature called the **native VLAN**.
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ISL does not have this feature
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- The native VLAN is VLAN 1 by default on all trunk ports, however this can be manually configured
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on each trunk port.
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- The switch does not ad an 802.1Q tag to frames in the native VLAN.
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- When a switch receives an untagged frame on a trunk port, it assumes the frame belongs to
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the native VLAN.
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**It's very important that the native VLAN matches!**
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## Trunk Configuration
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```Cisco
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SW1(config)#interface g0/0
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SW1(config-if)#switchport mode trunk
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command rejected
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```
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Many modern switches do not support Cisco;s ISL at all. They only support 802.1Q (dot1q)
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However, switches that do support both (like the one I'm using in this example) have a trunk
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encapsulation of Auto by default
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To manually configure the interface as a trunk port, you must first set the encapsulation to
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802.1Q or ISL. On switches that only support 802.1Q this is not necessary
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```Cisco
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SW1(config)#interface g0/0
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SW1(config-if)#switchport trunk encapsulation dot1q
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||||||
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SW1(config-if)#switchport mode trunk
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```
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To see the configurations about the trunk
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```Cisco
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SW1#show interfaces trunk
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Port Mode encapsulation Status Native vlan
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Gi0/0 on 802.1q trunking 1
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```
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```Cisco
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## for security reason you must not allow every vlan on the trunk
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SW1(config-if)#switchport trunk allowed vlan 10,30
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### for adding VLAN
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SW1(config-if)#switchport trunk allowed vlan add 20
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## For removing Vlan in the trunk use this command
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SW1(config-if)#switchport trunk allowed vlan remove 20
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### The all option is to allowed all vlan
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SW1(config-if)#switchport trunk allowed vlan all
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## The except command if for all vlan except a range or a specific vlan
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SW1(config-if)#switchport trunk allowed except 1-5,10
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## The none disable every VLAN
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SW1(config-if)#switchport trunk allowed none
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```
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For security purposes, it is best to change the native VLAN to an unused VLAN.
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(network security will be explained more-in depth later in the course)
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**Make sure the native VLAN matches on between switches**
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The command to change the native VLAN is :
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```Cisco
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SW1(config-if)#switchport trunk native vlan 1001
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|
```
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|
|
||||||
|
note : the show vlan brief command shows the access prots assigned to each VLAN, not
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|
the trunk ports that allow each VLAN.
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|
Use the **show interfaces trunk** command instead to confirm trunk ports.
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## ROAS (Router on a stick)
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For three VLAN in the same interface
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|
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|
```Cisco
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R1(config)#interface g0/0
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|
R1(config-if)#no shutdown
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|
R1(config-if)#interface g0/0.10
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R1(config-if)#encapsulation dot1q 10
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|
R1(config-subif)#ip address 192.168.1.62 255.255.255.192
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|
R1(config-if)#encapsulation dot1q 20
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|
R1(config-subif)#ip address 192.168.1.62 255.255.255.192
|
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|
R1(config-if)#encapsulation dot1q 30
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||||||
|
R1(config-subif)#ip address 192.168.1.62 255.255.255.192
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||||||
|
```
|
||||||
|
|
||||||
|
The subinterface number does not have to match the VLAN number.
|
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|
Howerver it is highly recommended that they do match, to make it easier to understand
|
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|
|
||||||
|
- ROAS is used to route beween multiple VLANs using a single interface on the router and switch.
|
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|
- The switch interface is configured as a regular trunk.
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- The router interface is configured using subinterfaces.
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|
- You configure the VLAN tag and IP address on each subinterface.
|
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|
- The router will behave as if frames arriving with a certain VLAN tag have arrived on the
|
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|
subinterface configured with that VLAN tag.
|
||||||
|
- The router will tag frames sent out of each subinterface with the VLAN tag configured on the
|
||||||
|
subinterface.
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|
|
||||||
|
## Review
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||||||
|
|
||||||
|
- What is a trunk port ?
|
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|
- What is the purpose of trunk ports?
|
||||||
|
- 802.1Q Encapsulation
|
||||||
|
- How to configure trunk ports
|
||||||
|
- 'Router on a Stick'(ROAS)
|
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90
18. VLAN (Part 3).md
Normal file
90
18. VLAN (Part 3).md
Normal file
@@ -0,0 +1,90 @@
|
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|
---
|
||||||
|
id: 1778493954-IJHJ
|
||||||
|
aliases:
|
||||||
|
- VLAN (Part 3)
|
||||||
|
tags: []
|
||||||
|
---
|
||||||
|
|
||||||
|
# VLAN (Part 3)
|
||||||
|
|
||||||
|
## Native VLAN on a router (ROAS)
|
||||||
|
|
||||||
|
There 2 methods for configuring the native VLAN on a router:
|
||||||
|
|
||||||
|
1.
|
||||||
|
```Cisco
|
||||||
|
R1(config)# int g0/0.10
|
||||||
|
R1(config-subif)#encapsulaton dot1q *vlan-id* native
|
||||||
|
```
|
||||||
|
|
||||||
|
2.
|
||||||
|
Configure the [[IP address]] for the native VLAN on the router's physical interface
|
||||||
|
(the command is not necessary)
|
||||||
|
```Cisco
|
||||||
|
R1(config)# int g0/0.10
|
||||||
|
R1(config-subif)#ip address 192.168.1.62 255.255.255.192
|
||||||
|
```
|
||||||
|
|
||||||
|
## Layer 3 (Multilayer) switches
|
||||||
|
|
||||||
|
- A multilayer switch is capable of both switching and routing.
|
||||||
|
- It is 'Layer 3 aware'
|
||||||
|
- You can assign IP addresses to its interfaces, like a router.
|
||||||
|
- You can create virtual interfaces for each VLAN, and assign IP addresses to those interfaces.
|
||||||
|
- You can configure routes on it, just like a router.
|
||||||
|
- it can be used for inter-VLAN routing
|
||||||
|
|
||||||
|
### Inter-VLAN routing via SVI
|
||||||
|
|
||||||
|
- SVIs (Switch Virtual Interfaces) are the virtual interfaces you can assign IP addresses to
|
||||||
|
in a multilayer switch.
|
||||||
|
- Configure each PC to use the SVI (Not the router) as their gateway address.
|
||||||
|
- To send traffic to different subnets/VLANs, the PCs will send traffic to the switch,
|
||||||
|
and the switch will route the traffic
|
||||||
|
|
||||||
|
the command to enable Layer 3 routing on the switch is
|
||||||
|
|
||||||
|
```Cisco
|
||||||
|
SW2(config)#ip routing
|
||||||
|
|
||||||
|
## this configure the interface as a 'routed port'
|
||||||
|
## (Layer 3 port, not Layer 2 /switchport)
|
||||||
|
SW2(config)#interface g0/1
|
||||||
|
SW2(config-if)#no switchport
|
||||||
|
|
||||||
|
## then you can configure an IP address on the interface like a regular router interface
|
||||||
|
SW2(config-if)#ip address 192.168.1.193 255.255.255.252
|
||||||
|
|
||||||
|
## then you can configure the default route
|
||||||
|
SW2(config-if)#ip route 0.0.0.0 0.0.0.0 192.168.1.194
|
||||||
|
```
|
||||||
|
|
||||||
|
To configure SVI you can assign ip address to each vlan
|
||||||
|
```Cisco
|
||||||
|
SW2(config)#interface vlan10
|
||||||
|
SW2(config-if)#ip address 192.168.1.62 255.255.255.192
|
||||||
|
SW2(config-if)#no shutdown
|
||||||
|
SW2(config)#interface vlan20
|
||||||
|
SW2(config-if)#ip address 192.168.1.126 255.255.255.192
|
||||||
|
SW2(config-if)#no shutdown
|
||||||
|
SW2(config)#interface vlan30
|
||||||
|
SW2(config-if)#ip address 192.168.1.190 255.255.255.192
|
||||||
|
SW2(config-if)#no shutdown
|
||||||
|
```
|
||||||
|
|
||||||
|
1. The Vlan must exist on the switch
|
||||||
|
2. The swithc must have at least one access port in the VLAN in an up/up state, AND/OR
|
||||||
|
one trunk port that allows the VLAN that is in an up/up state
|
||||||
|
3. The VLAN must not be shutdown (you can use the shutdown command to disable a VLAN)
|
||||||
|
4. The SVI must not be shutdown (SVIs are disabled by default)
|
||||||
|
|
||||||
|
## Review
|
||||||
|
|
||||||
|
- Native VLAN on a router
|
||||||
|
- Wireshark analysis
|
||||||
|
- Layer 3 Switching/multilayer Switching
|
||||||
|
|
||||||
|
**next lesson**
|
||||||
|
- DTP (Dynamic Trunking Protocol)
|
||||||
|
- VTP (VLAN trunking Protocol)
|
||||||
|
|
||||||
200
19. DTP - VTP.md
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19. DTP - VTP.md
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id: 19. DTP - VTP
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aliases: []
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tags: []
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---
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# DTP - VTP
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Note: DTP and VTP were removed from the CCNA exam topics list for the new exam (200-301).
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However, it's important to know their function, and you may still get questions about them
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on the exam even though they are not on the topics list
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## DTP Dynamic Trunking Protocol
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DTP is a [[Cisco]] proprietary protocol that allows Cisco switches to dynamically determine
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their interface status (access or trunk) without manual configuration
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DTP is enabled by default on all Cisco switch interfaces.
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So far, we have been manually configuring switchports using these command :
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- switchport mode access
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- switchport mode trunk
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For security purposes, manual configuration is recommended. DTP should be disabled on all switchports
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### CLI
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```Cisco
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SW2(config-if)#switchport mode ?
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## we will focus on the dynamic option
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SW2(config-if)#switchport mode dynamic ?
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## we have to mode auto or desirable
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```
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A switchport in dynamic desirable mode will actively try to form a trunk with other Cisco switches,
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it will form a trunk if connected to another switchport in the following modes:
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1. switchport mode trunk
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1. switchport mode dynamic desirable
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1. switchport mode dynamic auto
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to verify you can
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```Cisco
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SW1# show interfaces g0/0 switchport
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Name: Gi0/0
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Switchport: Enabled
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Administrative Mode: Dynamic desirable
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Operational Mode: trunk
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```
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### Static access
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Static access means an access port that belongs to a single VLAN that doesnt change (unless
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you configure a different VLAN).
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There are also 'dynamic access' ports, in which a server automatically assings the VLAN depending
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on the [[MAC]] address on the connected device.
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(This is out of the scope of the CCNA)
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| Administrative mode | Trunk | Dynamic desirable | Access | Dynamic Auto |
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| ------------- | -------------- | -------------- |------------ |------------ |
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| Trunk | Trunk | Trunk | x | Trunk|
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| Dynamic Desirable | Trunk | Trunk | Access | Trunk|
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| Access | x | Access | Access | Access |
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| Dynamic Auto | Trunk | Trunk | Access | Access |
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DTP will not form a trunk with a router, PC, etc.
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The switchport will be in access mode
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On *older* switches, **swithport mode dynamic desirable** is the default administrative mode.
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On *newer* switches, **swithport mode dynamic auto** is the default administrative mode.
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You can disable DTP negotiation on the interface with this command:
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- switchport nonegotiate
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Configuring an access port with **switchport mode access** also disables DTP negotiation on
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an interface
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It is recommended that you disable DTP on all switchports and manually confugre them as access or
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trunk ports.
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### Encapsulation
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[[Switches]] that support both [[802.1Q]] and ISL trunk encapsulations can use DTP to negotiate
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The encasulation they will use.
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This negotiation is enabled by default, as the default trunk encapsulation mode is :
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**switchport trunk encapsulation negotiate**
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*ISL is favored over 802.1Q, so if both switches support ISL, it will be selected*
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DTP frames are sent in VLAN1 when using ISL or in the [[native VLAN]] whe using 802.1Q
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(the default native VLAN is VLAN1, however)
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## VTP VLAN Trunking Protocol
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VTP allows you to configure VLANs on a central VTP server switch, and other switches (VTP client)
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will synchronize their VLAN database to the server.
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It is designed for large networks with many VLANs, so that you don't have to configure each VLAN
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on every switch
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It is rarely used, and it is recommended that you do not use it.
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There are three VTP versions: 1, 2, and 3.
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There are three VTP modes: server, client, and transparent.
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*Cisco switches operate in VTP server mode by default*
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### VTP Servers
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Can add/modify/delete VLANs
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Store the VLAN database in non-volatile RAM (NVRAM)
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Will increase the revision number every time a VLAN database on trunk interfaces, and
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The VTP clients will synchronize their VLAN database to it
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VTP servers also function as VTP client
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Therefore, A VTP server will synchronize to anothre VTP server with a higher revision number
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### VTP clients
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Cannot add/modify/delete VLANs
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Do not store the VLAN database in NVRAM (in VTPv3 they do)
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Will synchronize their VLAN database to the server with the highest revision number in their VTP domain
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Will advertise their VLAN database, and forward VTP advertisements to other client over their trunk
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ports.
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### How it's work
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to see all the VTP type
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```Cisco
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SW1#Show VTP status
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```
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VTPvv1/v2 do not support the extended VLAN range (1006-4094) only BTPv3 supports them
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to set a domain name
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```Cisco
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SW1#vtp domain cisco
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```
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now on switch 1 can do
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```Cisco
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SW1#vlan 10
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SW1#name engineering
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```
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switch 2 will have the same vtp domain and vlan configured
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pass along to switch 3 and 4
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If a switch with no VTP domain (domain NULL) receives a VTP advertisement with a VTP domain name,
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it will automatically join that VTP domain
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If a switch receives a VTP advertisement in the same VTP domain with a higher revision number
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it will update its VLAN database to match
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### **ONE DANGER OF VTP**
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If you connect an old switch with a higher revision number to your network ( and the VTP domain
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matches), all switches in the domain will sync their VLAN database to that switch
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### VTP transparent mode
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Does not participate in the VTP domain (does not sync its VLAN database).
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Maintains its own VLAN database in NVRAM. it can add/modify/delete VLANs, byt they won't be
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advertised to other switches.
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Will forward VTP advertisements that are in the same domain as it.
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NOTE : Changing the VTP domain to an unused domain will reset the revision number to 0
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Changing the VTP mode to transparent will also reset the revision number to 0
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### VTP version
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You can change the VTP version with this command
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```Cisco
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SW1(config)#vtp version 2
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```
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VTP V2 is not much different than VTP V1. The major difference is that VTP V2 introduces support
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for Token RIng VLANs. if you use Token Ring VLANs, you must enable VTP V2. Otherwise there is
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no reason to use VTP V2
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For the V3 it's Beyond the scope of the CCNA
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|
# Review
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||||||
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note: Recommended that you disable this protocol for security purposes.
|
||||||
|
|
||||||
|
DTP (dynamic trunking Protocol)
|
||||||
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a protocol that allows Cisco switches to form trunk connections with other cisco switch without
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manual configuration
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||||||
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VTP (VLAN Trunking Protocol)
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||||||
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Allow to configure VLAN on switches that operate as central VTP servers, which then advertise
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Their VLAN database,and VTP client switches sync their database to it
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Reference in New Issue
Block a user