add DTP VLAN and Subnetting
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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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note: Recommended that you disable this protocol for security purposes.
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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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VTP (VLAN Trunking Protocol)
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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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