Can switch in Transparent VTP mode be root bridge?

Answered Question
Mar 9th, 2009

Hi all

i have switch config here

sh vtp status

VTP Version : 2

Configuration Revision : 0

Maximum VLANs supported locally : 1005

Number of existing VLANs : 6

VTP Operating Mode : Transparent

VTP Domain Name : NMLYB_MID

VTP Pruning Mode : Disabled

VTP V2 Mode : Disabled

VTP Traps Generation : Enabled

MD5 digest : 0xA2 0x66 0x3E 0x06 0x0C 0xC0 0x81 0x21

Configuration last modified by 0.0.0.0 at 0-0-00 00:00:00

As per config it is in Transparent mode.

NExt

sh spanning-tree

VLAN0001

Spanning tree enabled protocol ieee

Root ID Priority 32769

Address 001d.45d1.e800

This bridge is the root

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)

Address 001d.45d1.e800

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 300

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Gi1/0/1 Desg FWD 4 128.1 P2p

Fa1/0/16 Desg FWD 100 128.18 Shr

VLAN0005

Spanning tree enabled protocol ieee

Root ID Priority 32773

Address 001d.45d1.e800

This bridge is the root

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32773 (priority 32768 sys-id-ext 5)

Address 001d.45d1.e800

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 300

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Gi1/0/1 Desg FWD 4 128.1 P2p

nmlybs2#

here it shows it is root bridge also.

so my question is can switch in transparent vto mode can be root bridge.

many thanks

I have this problem too.
0 votes
Correct Answer by Jon Marshall about 7 years 9 months ago

Mat

A switch in VTP transparent mode has it's own vlan database. This vlan database is not sent to any other switches and any VTP updates the transparent mode switch receives it does not use to update it's own vlan database but it will forward them on to other switches.

So yes it is responsible for it's own local vlan database.

Jon

Correct Answer by Jon Marshall about 7 years 9 months ago

Mahesh

all other switches will try to reach it

as this is Root bridge for STP.

Well the root bridge is only used for the creation of a loop free topology. So once the topology has been decided on the path the traffic takes does not necessarily have to go through the root bridge.

Vlan updates are sent by VTP servers, altho there is a rare case where a VTP client can actually overwrite the VTP database but this is not normal operation.

Jon

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Jon Marshall Mon, 03/09/2009 - 10:39

Mahesh

Well your config kind of proves it can be :-).

Yes, there is no reason why a switch running in VTP transparent mode cannot be the root bridge for some or all of your vlans.

Jon

mahesh18 Mon, 03/09/2009 - 11:14

Hi jon,

so in this case mu understaning is that

all other switches will try to reach it

as this is Root bridge for STP.

And VLan updates will be send only by

switch in VTP server mode right?

thanks

Correct Answer
Jon Marshall Mon, 03/09/2009 - 11:28

Mahesh

all other switches will try to reach it

as this is Root bridge for STP.

Well the root bridge is only used for the creation of a loop free topology. So once the topology has been decided on the path the traffic takes does not necessarily have to go through the root bridge.

Vlan updates are sent by VTP servers, altho there is a rare case where a VTP client can actually overwrite the VTP database but this is not normal operation.

Jon

mattkaya56 Mon, 03/09/2009 - 16:41

Hello Jon,

Hope I can a question?

When a switch is in transparent mode by default it is the server for its own(local) vlans except in this case that the server does not propagate the local vlan database to other switches - correct?

Thanks in advance

Mat

adamclarkuk_2 Mon, 03/09/2009 - 16:48

Hi Matt

When you set the VTP mode to transparent, then the switches do not participate in VTP.

A VTP transparent switch will not advertise its VLAN configuration and does not synchronize its VLAN configuration from received messages. VLANS can be created, changed or deleted when in transparent mode.

In VTP v 2, transparent switches do forward VTP messages that they receive out their trunk ports.

Correct Answer
Jon Marshall Mon, 03/09/2009 - 16:48

Mat

A switch in VTP transparent mode has it's own vlan database. This vlan database is not sent to any other switches and any VTP updates the transparent mode switch receives it does not use to update it's own vlan database but it will forward them on to other switches.

So yes it is responsible for it's own local vlan database.

Jon

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