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Bronze

vtp version1,2 and transparent mode

Hi every body!

According to my book,in vtp version 1, switch in transparent mode must have the same domain name and run the same version i.e version 1 to relay vtp messages.

lets take the following scenario

sw1---------sw2----------sw3

sw1 and sw2 and sw3 are running version 2.

sw1 is vtp server,domain name cisco

sw2 is vtp transparent ,domain name=null

sw3 is vtp client, domain name cisco

Now we enable version 1 on sw1(vtp server)

What would sw2(vtp transparent) would do?

will it switch to version 1? if yes, it would not be able to relay as mentioned above, with domain name=null, sw2 does not match the domain name cisco, thus can not relay the vtp advertisements to sw3.

Am i correct?

thanks a lot!

3 ACCEPTED SOLUTIONS

Accepted Solutions
Hall of Fame Super Silver

Re: vtp version1,2 and transparent mode

Hello Sarah,

being Sw2 in vtp transparent mode it will stay in VTP version2 and it will still propagate VTP updates sent by SW1 to SW3 even if VTP domain name doesn't match.

SW3 being a VTP client will receive the update and will change to VTP version 1.

A VTP transparent switch never applies to itself the contents of VTP updates, it just propagates them to other devices.

It is true that VTP vers. 1 transparent switch checks the VTP domain name in updates with its own if it doesn't match updates are not propagated.

Hope to help

Giuseppe

Hall of Fame Super Bronze

Re: vtp version1,2 and transparent mode

According to my book,in vtp version 1, switch in transparent mode must have the same domain name and run the same version i.e version 1 to relay vtp messages.

It has to have the same domain-name but it does not need the same VTP Version.

SW1(VTP Server):

Rack1SW1#sh vtp status

VTP Version : 2

Configuration Revision : 4

Maximum VLANs supported locally : 1005

Number of existing VLANs : 24

VTP Operating Mode : Server

VTP Domain Name : cisco

VTP Pruning Mode : Disabled

VTP V2 Mode : Enabled

VTP Traps Generation : Disabled

SW2 (Transparent Running V1):

Rack1SW2#sh vtp status

VTP Version : 2

Configuration Revision : 0

Maximum VLANs supported locally : 1005

Number of existing VLANs : 24

VTP Operating Mode : Transparent

VTP Domain Name : cisco

VTP Pruning Mode : Disabled

VTP V2 Mode : Disabled

VTP Traps Generation : Disabled

SW3(VTP Client):

Rack1SW3#sh vtp st

VTP Version : 2

Configuration Revision : 4

Maximum VLANs supported locally : 1005

Number of existing VLANs : 24

VTP Operating Mode : Client

VTP Domain Name : cisco

VTP Pruning Mode : Disabled

VTP V2 Mode : Enabled

VTP Traps Generation : Disabled

Now, let's see if the VTP updates traverse via the transparent switch:

Current Status

Rack1SW1#sh vtp st

VTP Version : 2

Configuration Revision : 4

Maximum VLANs supported locally : 1005

Number of existing VLANs : 24

VTP Operating Mode : Server

VTP Domain Name : cisco

VTP Pruning Mode : Disabled

VTP V2 Mode : Enabled

VTP Traps Generation : Disabled

MD5 digest : 0x20 0xA7 0xAE 0x02 0xDD 0x68 0xD4 0xCE

Configuration last modified by 10.1.37.7 at 3-12-93 17:09:10

Local updater ID is 10.1.37.7 on interface Fa0/3 (first layer3 interface found)

!

!

!

Rack1SW1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

Rack1SW1(config)#no vlan 78

Rack1SW1(config)#exit

Rack1SW1#

!

!

!

1w4d: %SYS-5-CONFIG_I: Configured from console by console

Rack1SW1#sh vtp st

VTP Version : 2

Configuration Revision : 5

Maximum VLANs supported locally : 1005

Number of existing VLANs : 23

VTP Operating Mode : Server

VTP Domain Name : cisco

VTP Pruning Mode : Disabled

VTP V2 Mode : Enabled

VTP Traps Generation : Disabled

MD5 digest : 0xB3 0xF1 0x27 0x01 0x67 0x56 0x69 0xD4

Configuration last modified by 10.1.37.7 at 3-12-93 17:13:00

Local updater ID is 10.1.37.7 on interface Fa0/3 (first layer3 interface found)

Rack1SW1#

Rack9Pod1>3

!

!

!

[Resuming connection 3 to sw3 ... ]

Rack1SW3#sh vtp status

VTP Version : 2

Configuration Revision : 5

Maximum VLANs supported locally : 1005

Number of existing VLANs : 23

VTP Operating Mode : Client

VTP Domain Name : cisco

VTP Pruning Mode : Disabled

VTP V2 Mode : Enabled

VTP Traps Generation : Disabled

MD5 digest : 0xB3 0xF1 0x27 0x01 0x67 0x56 0x69 0xD4

Configuration last modified by 10.1.37.7 at 3-12-93 17:13:00

Rack1SW3#

HTH,

__

Edison.

Hall of Fame Super Bronze

Re: vtp version1,2 and transparent mode

1) in your reply, I find the config revision=0 on transparent switch though switch has 24 vlans. The question is how is it possible for a switch in transparent mode to have 24 vlans cconfigured but yet config reviion=o?

config revision set to 0 is the net result of changing the VTP domain name. I changed it during my test in order to prove that VTP traffic won't traverse via this switch if the domain name do not match.

2)So switch in transparent mode running version 1, will pass vtp messages from switch in server mode, running version 2 If:

domain name matches.

How about if sw2(transparent switch) has default domain name=null,and running version 1, will it pass the vtp messages to sw3?

I'll have to test for that scenario (I won't have time until Tuesday) but I believe it won't work, as Giuseppe indicated - it needs to have v2 enabled for it to work.

__

Edison.

13 REPLIES

Re: vtp version1,2 and transparent mode

Hi Sarah,

In the real world, we always ensure all switches are running the same VTP version.

However, theoretically in the above case, sw1 is only running VTP version 1. But since the transparent switch in the middle is running version 2, it should simply forward VTP messages (even though its domain name does not match the sw1's). The transparent switch will never change its version. So, sw3 should receive VTP messages.

HTH

Lejoe

Re: vtp version1,2 and transparent mode

Hi,

I think the Sw2 should be in the same vtp domain as the other switches orelse it will not forward the advertisements.

Thanks

Mahmood

Hall of Fame Super Silver

Re: vtp version1,2 and transparent mode

Hello Sarah,

being Sw2 in vtp transparent mode it will stay in VTP version2 and it will still propagate VTP updates sent by SW1 to SW3 even if VTP domain name doesn't match.

SW3 being a VTP client will receive the update and will change to VTP version 1.

A VTP transparent switch never applies to itself the contents of VTP updates, it just propagates them to other devices.

It is true that VTP vers. 1 transparent switch checks the VTP domain name in updates with its own if it doesn't match updates are not propagated.

Hope to help

Giuseppe

New Member

Re: vtp version1,2 and transparent mode

Hi Giuseppe,

Allow me to quote you:

"being Sw2 in vtp transparent mode it will stay in VTP version2 and it will still propagate VTP updates sent by SW1 to SW3 even if VTP domain name doesn't match."

I tried this in a lab yesterday. I found that SW2 must be in the samed VTP domain as server and client in order to forward VTP info from the server to the client.

Hall of Fame Super Silver

Re: vtp version1,2 and transparent mode

Hello Wassim,

I couldn't test the proposed scenario at the time of my answer that is based on theory and some experience.

A VTP client switch reverts to the VTP version it sees in VTP updates.

A version2 (enabled locally on device) VTP transparent switch should be able to forward VTP updates even if the domain doesn't match.

Because it doesn't apply to itself the VTP update it shouldn't revert to VTP version 1 as stated in the VTP update.

See Peter's post about his tests it looks like to confirm the behaviour of a version1 VTP transparent switch.

So in the tests it's important to start from a scenario with VTP version 2 on all switches.

Then move sw2 to vtp transparent mode and change its domain name.

After this on sw1 the VTP server changes to VTP version1.

if SW3 reverts to version 1 this means the update has gone through SW2.

I've noticed that VTP can take time to see changes on downstream devices so wait some time and check with sh vtp status.

Hope to help

Giuseppe

Hall of Fame Super Bronze

Re: vtp version1,2 and transparent mode

According to my book,in vtp version 1, switch in transparent mode must have the same domain name and run the same version i.e version 1 to relay vtp messages.

It has to have the same domain-name but it does not need the same VTP Version.

SW1(VTP Server):

Rack1SW1#sh vtp status

VTP Version : 2

Configuration Revision : 4

Maximum VLANs supported locally : 1005

Number of existing VLANs : 24

VTP Operating Mode : Server

VTP Domain Name : cisco

VTP Pruning Mode : Disabled

VTP V2 Mode : Enabled

VTP Traps Generation : Disabled

SW2 (Transparent Running V1):

Rack1SW2#sh vtp status

VTP Version : 2

Configuration Revision : 0

Maximum VLANs supported locally : 1005

Number of existing VLANs : 24

VTP Operating Mode : Transparent

VTP Domain Name : cisco

VTP Pruning Mode : Disabled

VTP V2 Mode : Disabled

VTP Traps Generation : Disabled

SW3(VTP Client):

Rack1SW3#sh vtp st

VTP Version : 2

Configuration Revision : 4

Maximum VLANs supported locally : 1005

Number of existing VLANs : 24

VTP Operating Mode : Client

VTP Domain Name : cisco

VTP Pruning Mode : Disabled

VTP V2 Mode : Enabled

VTP Traps Generation : Disabled

Now, let's see if the VTP updates traverse via the transparent switch:

Current Status

Rack1SW1#sh vtp st

VTP Version : 2

Configuration Revision : 4

Maximum VLANs supported locally : 1005

Number of existing VLANs : 24

VTP Operating Mode : Server

VTP Domain Name : cisco

VTP Pruning Mode : Disabled

VTP V2 Mode : Enabled

VTP Traps Generation : Disabled

MD5 digest : 0x20 0xA7 0xAE 0x02 0xDD 0x68 0xD4 0xCE

Configuration last modified by 10.1.37.7 at 3-12-93 17:09:10

Local updater ID is 10.1.37.7 on interface Fa0/3 (first layer3 interface found)

!

!

!

Rack1SW1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

Rack1SW1(config)#no vlan 78

Rack1SW1(config)#exit

Rack1SW1#

!

!

!

1w4d: %SYS-5-CONFIG_I: Configured from console by console

Rack1SW1#sh vtp st

VTP Version : 2

Configuration Revision : 5

Maximum VLANs supported locally : 1005

Number of existing VLANs : 23

VTP Operating Mode : Server

VTP Domain Name : cisco

VTP Pruning Mode : Disabled

VTP V2 Mode : Enabled

VTP Traps Generation : Disabled

MD5 digest : 0xB3 0xF1 0x27 0x01 0x67 0x56 0x69 0xD4

Configuration last modified by 10.1.37.7 at 3-12-93 17:13:00

Local updater ID is 10.1.37.7 on interface Fa0/3 (first layer3 interface found)

Rack1SW1#

Rack9Pod1>3

!

!

!

[Resuming connection 3 to sw3 ... ]

Rack1SW3#sh vtp status

VTP Version : 2

Configuration Revision : 5

Maximum VLANs supported locally : 1005

Number of existing VLANs : 23

VTP Operating Mode : Client

VTP Domain Name : cisco

VTP Pruning Mode : Disabled

VTP V2 Mode : Enabled

VTP Traps Generation : Disabled

MD5 digest : 0xB3 0xF1 0x27 0x01 0x67 0x56 0x69 0xD4

Configuration last modified by 10.1.37.7 at 3-12-93 17:13:00

Rack1SW3#

HTH,

__

Edison.

Bronze

Re: vtp version1,2 and transparent mode

Thanks for your reply Edison.

I have few questions:

1) in your reply, I find the config revision=0 on transparent switch though switch has 24 vlans. The question is how is it possible for a switch in transparent mode to have 24 vlans cconfigured but yet config reviion=o?

2)So switch in transparent mode running version 1, will pass vtp messages from switch in server mode, running version 2 If:

domain name matches.

How about if sw2(transparent switch) has default domain name=null,and running version 1, will it pass the vtp messages to sw3?

thanks a lot!

Hall of Fame Super Bronze

Re: vtp version1,2 and transparent mode

1) in your reply, I find the config revision=0 on transparent switch though switch has 24 vlans. The question is how is it possible for a switch in transparent mode to have 24 vlans cconfigured but yet config reviion=o?

config revision set to 0 is the net result of changing the VTP domain name. I changed it during my test in order to prove that VTP traffic won't traverse via this switch if the domain name do not match.

2)So switch in transparent mode running version 1, will pass vtp messages from switch in server mode, running version 2 If:

domain name matches.

How about if sw2(transparent switch) has default domain name=null,and running version 1, will it pass the vtp messages to sw3?

I'll have to test for that scenario (I won't have time until Tuesday) but I believe it won't work, as Giuseppe indicated - it needs to have v2 enabled for it to work.

__

Edison.

Bronze

Re: vtp version1,2 and transparent mode

Thanks a lot Edison and have a good day!

Bronze

Re: vtp version1,2 and transparent mode

Edison,

As far as I am aware the config revision = 0 is the result of setting vtp mode to transparent.

That is the way I always have been told to make sure that I do not put a switch on the network with a higher revision number: Change to transparent mode which resets revisionnumber to 0 and then change to either server or client mode.

Have I been told wrongly?

Regards, Ingolf

Cisco Employee

Re: vtp version1,2 and transparent mode

Ingolf,

You have been told correctly. However, the VTP revision number is indeed reset to 0 when you change the domain name or when you select the VTP Transparent mode. Both these changes lead to the revision number being zeroed.

Best regards,

Peter

Hall of Fame Super Bronze

Re: vtp version1,2 and transparent mode

Now we enable version 1 on sw1(vtp server)

What would sw2(vtp transparent) would do?

will it switch to version 1?

When changing VTP version on the VTP server, it only affects other switches participating in the VTP domain. When you make a switch transparent, it isn't participating in the VTP domain, so any changes made in the VTP domain aren't made on this switch.

Keep in mind, switches - by default - will operate in Version 1 even though the version in the show vtp status output states Version 2. You need to look at the VTP V2 Mode entry to identify what version the switch is running.

Please refer to the documentation for more info:

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_46_se/command/reference/cli2.html#wp1950626

HTH,

__

Edison.

Cisco Employee

Re: vtp version1,2 and transparent mode

Sarah, Edison, Giuseppe,

Please allow me to add my two cents. I was doing experiments with VTP Version 1. I have observed that a switch in VTP Transparent mode forwards VTP messages under these two circumstances:

1.) The VTP domain name on the Transparent switch is set to NULL (it is unset). In this case, it does not have to match the domain name of the neighboring switches. The neighboring switches can be set any domain name.

2.) If the VTP domain name is set (i.e. is not NULL) on the Transparent switch, it must match the VTP domain name of the neighboring switches.

Frankly, the VTP Transparent behavior seems to me to be pretty confusing :-(

Best regards,

Peter

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