How VTP is transport on the trunk

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Jul 16th, 2010
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Hi,


Does anybody knows how VTP protocol is transported over a trunk. Is it carry on default VLAN 1, what is happening to VTP when native VLAN is not configured on VLAN 1? Can a misconfiguration on default VLAN 1 cause problem to VTP?


Also would like to know if there is a system message associate to VLAN 1 being down. I saw on a CCNA test question where there was a message about problem with default or VLAN 1.


Thanks

Stephane

Hi ,

native vlan mean the trunk port will not tagged the packet with vlan No.
for example : 2 switches connect by trunk and you configure in sw 1 native vlan 2 and sw 2 native vlan is vlan 1
then you will get error native vlan mismatch , that mean must native vlan in sw 1 and 2 is the same vlan

by default all control messages (STP , VTP , ...) is send it between switches by vlan 1
and the default if configure a trunk port native is VLAN 1 (you dont need to configure it)

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Correct Answer

Hi ,

native vlan mean the trunk port will not tagged the packet with vlan No.
for example : 2 switches connect by trunk and you configure in sw 1 native vlan 2 and sw 2 native vlan is vlan 1
then you will get error native vlan mismatch , that mean must native vlan in sw 1 and 2 is the same vlan

by default all control messages (STP , VTP , ...) is send it between switches by vlan 1
and the default if configure a trunk port native is VLAN 1 (you dont need to configure it)

Ganesh Hariharan Sat, 07/17/2010 - 01:10
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Hi,


Does anybody knows how VTP protocol is transported over a trunk. Is it carry on default VLAN 1, what is happening to VTP when native VLAN is not configured on VLAN 1? Can a misconfiguration on default VLAN 1 cause problem to VTP?


Also would like to know if there is a system message associate to VLAN 1 being down. I saw on a CCNA test question where there was a message about problem with default or VLAN 1.


Thanks

Stephane


Hi Stephane,


VTP messages always travel over the default VLAN for the media. For example, on an Ethernet trunk, VTP transports over VLAN 1; on FDDI, it transports over VLAN 1002; and over ATM, VTP transports over ELAN default. Because you cannot delete any of the default VLANs, VTP messages always propagate over LAN trunk ports.


VTP provides a communication protocol between Catalysts over trunks. The protocol allows Catalysts to share information about VLANs in the VTP management domain. VTP operates only after DISL/DTP complete the trunk negotiation process and functions as a payload of ISL/802.1Q. VTP does not work over non-trunk ports. Therefore, it cannot send/receive any messages until DISL or DTP negotiate a link into trunk status. VTP works separately from ISL and 802.1Q in that VTP messages transport configuration data, whereas ISL and 802.1Q specify encapsulation methods


Hope to Help !!


Ganesh.H


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