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Bronze

vtp transparent mode version 1, check version and domain

HI  everybody

My book says a  switch in vtp transparent mode, does not apply the vtp messages to itself,rather it just passes them. Below in my lab, I found out a switchin transparent mode running  vtp default version which is 1,  with" null" as domain name , changes its domain name to " cisco" upon receiving vtp advertisements.   Below is the setup with" show vtp status output".

R1(vtp server)--------vtp domain cisco --R2( vtp  transparent)-----vtp domain cisco-----R3(vtp client)

When I run VTp version 1 on in the above case with  R1 and R3  configured as vtp domain cisco, vtp server and cleint respectively and R2 as vtp transparent mode ,with default settings which means vtp domain null.  I noticed that R2 changed its domain from null to cisco.  My question is why  did R2 ( vtp transparent mode) change its domain name from null to cisco ?

Please consider the above set up.

This time  I changed the vtp version from default ( vtp ver 1) to version 2. on R1(server) while R2 is still running default version 1.

R1's show vtp status output:

R1#show vtp status

VTP Version                     : 2

Configuration Revision          : 4

Maximum VLANs supported locally : 36

Number of existing VLANs        : 8

VTP Operating Mode              : Server

VTP Domain Name                 : cisco

VTP Pruning Mode                : Disabled

VTP V2 Mode                     : Enabled

VTP Traps Generation            : Disabled

MD5 digest                      : 0x28 0x3A 0x64 0x0F 0xBB 0xB4 0x64 0x0C

Configuration last modified by 0.0.0.0 at 3-1-02 00:24:52

Local updater ID is 0.0.0.0 (no valid interface found)

R2( vtp transparent)'s show vtp status output:

R2#show vtp status

VTP Version                     : 2

Configuration Revision          : 0

Maximum VLANs supported locally : 36

Number of existing VLANs        : 5

VTP Operating Mode              : Transparent

VTP Domain Name                 : cisco

VTP Pruning Mode                : Disabled

VTP V2 Mode                     : Disabled

VTP Traps Generation            : Disabled

MD5 digest                      : 0x89 0x5D 0x37 0xD0 0x91 0x71 0xF7 0x96

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

R2#

R3( client) 's  show vtp status output:

R3#show vtp status

VTP Version                     : 2

Configuration Revision          : 4

Maximum VLANs supported locally : 36

Number of existing VLANs        : 8

VTP Operating Mode              : Client

VTP Domain Name                 : cisco

VTP Pruning Mode                : Disabled

VTP V2 Mode                     : Enabled

VTP Traps Generation            : Disabled

MD5 digest                      : 0x28 0x3A 0x64 0x0F 0xBB 0xB4 0x64 0x0C

Configuration last modified by 0.0.0.0 at 3-1-02 00:24:52

Notice that confiig revision number is 4 at R1( server)  and R3 client.  Next i will configure vlan 8 on R1(server) to increase config revsion number and see if R2( transparent) running default vtp version 1 passes these vtp advertisements to R3 ( client)

After i configure vlan 8, the config revision number jumps to 5 from 4.

R1#show vtp status

VTP Version                     : 2

Configuration Revision          : 5

Maximum VLANs supported locally : 36

Number of existing VLANs        : 9

VTP Operating Mode              : Server

VTP Domain Name                 : cisco

VTP Pruning Mode                : Disabled

VTP V2 Mode                     : Enabled

VTP Traps Generation            : Disabled

MD5 digest                      : 0xFE 0x7A 0x14 0x44 0x4F 0xF2 0x5A 0x50

Configuration last modified by 0.0.0.0 at 3-1-02 00:30:1

Next i will check  R2 too see if it has received any vtp advertisements.

R3#show vtp status

VTP Version                     : 2

Configuration Revision          : 5

Maximum VLANs supported locally : 36

Number of existing VLANs        : 9

VTP Operating Mode              : Client

VTP Domain Name                 : cisco

VTP Pruning Mode                : Disabled

VTP V2 Mode                     : Enabled

VTP Traps Generation            : Disabled

MD5 digest                      : 0xFE 0x7A 0x14 0x44 0x4F 0xF

Note config revision has jumped to 5 from 4.  It implies  R2 must have passed the vtp advertisements to R3.

The question is why?

Because my book says a switch in vtp transparent mode running vtp version 1, checks version number and domain against its own, if they match , it will relays the message to other switches. In our case  R2 has relayed the vtp advertisements to R3 although it is running default vtp version 1.  Is this some bug in ios?

Thanks and have a great day.

4 REPLIES
Bronze

vtp transparent mode version 1, check version and domain

Hi everybody.

I found some info; I am posting it here for someone who might have the similar question.

VTP version 1 checks only domain name not version  as my book and some links erroneously mention.

VTP version 2 does not check domain name.

A switch in transparent mode with default domain name " null" changes its domain to one specified in the received vtp advertisement. Other than that,  a switch in vtp client mode does not apply any configurations carried in a vtp advertisements; It simply relays them.

You guys have a great weekend.

New Member

vtp transparent mode version 1, check version and domain

Hi,

First, your output shows you are running VTP version 2 (R2), and below statements differ VTP version 1 and 2,

VTP v1, a transparent mode switch does not even relay VTP information it receives to other switches unless its VTP domain names and VTP version numbers match those of the other switches.

VTP v2, transparent switches do forward recieved VTP advertisements out their trunk ports, acting as VTP relays. This occurs regardless of the VTP domain name setting.

May be it is a IOS bug in your switches and check Software Bug Toolkit of Cisco.

HTH

Bronze

vtp transparent mode version 1, check version and domain

Thanks Shirkul.

I will get back to you with my lab results tomorrow.

Have a nice weekend.

Bronze

Re: vtp transparent mode version 1, check version and domain

Hi

I apologies for the late reply.

Below is the lab set-up

All switches are vtp in domain Cisco.

sw1( vtp server, vtp version 2)---------------Sw2( vtp transparent,version 1)--------------sw3( vtp client, version 2)

sw1#show vtp status

VTP Version                     : 2

Configuration Revision          : 1

Maximum VLANs supported locally : 36

Number of existing VLANs        : 5

VTP Operating Mode              : Server

VTP Domain Name                 : cisco

VTP Pruning Mode                : Disabled

VTP V2 Mode                     : Enabled

VTP Traps Generation            : Disabled

MD5 digest                      : 0x32 0xF9 0x20 0xBF 0xAB 0x8D 0xF6 0xB7

Configuration last modified by 0.0.0.0 at 3-1-02 00:02:56

Local updater ID is 0.0.0.0 (no valid interface found)

==========================================================

sw2#show vtp status

VTP Version                     : 2

Configuration Revision          : 0

Maximum VLANs supported locally : 36

Number of existing VLANs        : 5

VTP Operating Mode              : Transparent

VTP Domain Name                 : cisco

VTP Pruning Mode                : Disabled

VTP V2 Mode                     : Disabled

VTP Traps Generation            : Disabled

MD5 digest                      : 0x89 0x5D 0x37 0xD0 0x91 0x71 0xF7 0x96

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

=============================================================

sw3#show vtp status

VTP Version                     : 2

Configuration Revision          : 1

Maximum VLANs supported locally : 36

Number of existing VLANs        : 5

VTP Operating Mode              : Client

VTP Domain Name                 : cisco

VTP Pruning Mode                : Disabled

VTP V2 Mode                     : Enabled

VTP Traps Generation            : Disabled

MD5 digest                      : 0x32 0xF9 0x20 0xBF 0xAB 0x8D 0xF6 0xB7

Configuration last modified by 0.0.0.0 at 3-1-02 00:02:56

==================================================================

Next I will create a vlan 2 at sw1 to bump the config revision number up

sw1(config)#vlan 2

sw1(config-vlan)#exit

sw1(config)#end

R1#show

*Mar  1 00:10:18.935: %SYS-5-CONFIG_I: Configured from console by console

sw1#show vtp status

VTP Version                     : 2

Configuration Revision          : 2

Maximum VLANs supported locally : 36

Number of existing VLANs        : 6

VTP Operating Mode              : Server

VTP Domain Name                 : cisco

VTP Pruning Mode                : Disabled

VTP V2 Mode                     : Enabled

VTP Traps Generation            : Disabled

MD5 digest                      : 0x35 0x84 0x7B 0x04 0x3D 0x55 0x3B 0xDA

Configuration last modified by 0.0.0.0 at 3-1-02 00:10:16

Local updater ID is 0.0.0.0 (no valid interface found)

Next I check at sw3 if it receives an vtp advertisement.

sw3#show vtp status

VTP Version                     : 2

Configuration Revision          : 2

Maximum VLANs supported locally : 36

Number of existing VLANs        : 6

VTP Operating Mode              : Client

VTP Domain Name                 : cisco

VTP Pruning Mode                : Disabled

VTP V2 Mode                     : Enabled

VTP Traps Generation            : Disabled

MD5 digest                      : 0x35 0x84 0x7B 0x04 0x3D 0x55 0x3B 0xDA

Configuration last modified by 0.0.0.0 at 3-1-02 00:10:16

Indeed, sw3 received an vtp advertisement and increased its config revision number to 2.  It implies  sw2 ( transparent mode) receives vtp advertisement from sw1(server) and forwards it to SW3( client)

eventhough sw2 running vtp version 1 and sw1 and sw3 are running vtp version 2.

thanks and have a great weekend.

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