VTP version mismatch

Came across a question in the Boson OCG paractice set that says a switch configured as a vtp server in version 1 will not be able to form an active vtp domain with a switch that is a vtp client running version 2.

I labbed it up on 2 3550s and lo and behold, the client that was configured for vtp version 2 downgraded to vtp version 1 automactically and began exchanging VLAN information. Is this an anomoly or is the question wrong?

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Todd Burrell

I believe if the VTP server is version 2 and the client is version 1 that would not work? And I don't think that version 1 transparent switches will pass along info to upper level VTP servers and clients. But this is all conjecture as I have not researched it that much - this is just from memory of the CCNA exam studying.

vinbuck

If the server is version 2 and the client is version 1, the server will bring the client up to version 2 automatically...just checked it on a pair of 3550s. Either way it seems that the client will match what the server is using and you can't change the version on the client side

reloaded

As I recall, VTP v1 and v2 are not interoperable. So VTP should come up with the one that is compatible...in this case, its version one.

SubnetZero

I have four switches (SW1,SW2,SW3,SW4) all connected to one another using Gig0/19-24 (please see CDP table from SW1)

SW1(config)#do sh cdp ne | i SW
SW4              Gig 0/22          171          R S I     WS-C3560G Gig 0/22
SW4              Gig 0/21          171          R S I     WS-C3560G Gig 0/21
SW2              Gig 0/24          167           S I      WS-C3560G Gig 0/24
SW2              Gig 0/23          167           S I      WS-C3560G Gig 0/23
SW3              Gig 0/20          173          R S I     WS-C3560G Gig 0/20
SW3              Gig 0/19          173          R S I     WS-C3560G Gig 0/19

So you can see that SW1 has connections to all of the other switches and they are trunked as well

SW1(config)#do sh inter trunk
Port        Mode             Encapsulation  Status        Native vlan
Gi0/19      on               802.1q         trunking      1
Gi0/20      on               802.1q         trunking      1
Gi0/21      on               802.1q         trunking      1
Gi0/22      on               802.1q         trunking      1
Gi0/23      on               802.1q         trunking      1
Gi0/24      on               802.1q         trunking      1

In this example SW1 will be the VTP server in VTP domain CCIE with a VTP password of CCIE running in VTP version 2.

SW2 will be a VTP client running in VTP version 1 and SW3 will be running in transparent mode VTP version 1.

SW1(config)#do sh vtp status
[COLOR=#0000cd][B]VTP Version                     : running VTP1 (VTP2 capable)[/B]
[/COLOR]Configuration Revision          : 0
Maximum VLANs supported locally : 1005
Number of existing VLANs        : 16
[COLOR=#0000cd][B]VTP Operating Mode              : Server[/B]
[/COLOR]VTP Domain Name                 : CCIE
VTP Pruning Mode                : Disabled
[COLOR=#0000cd][B]VTP V2 Mode                     : Disabled[/B]
[/COLOR]VTP Traps Generation            : Disabled
MD5 digest                      : 0x23 0xE7 0x2E 0xA4 0x68 0xC5 0xC7 0x4A

SW2(config)#do sh vtp status
[COLOR=#0000cd][B]VTP Version                     : running VTP1 (VTP2 capable)[/B]
[/COLOR]Configuration Revision          : 0
Maximum VLANs supported locally : 1005
Number of existing VLANs        : 16
[COLOR=#0000cd][B]VTP Operating Mode              : Client[/B]
[/COLOR]VTP Domain Name                 : CCIE
VTP Pruning Mode                : Disabled
[COLOR=#0000cd][B]VTP V2 Mode                     : Disabled[/B]
[/COLOR]VTP Traps Generation            : Disabled
MD5 digest                      : 0x23 0xE7 0x2E 0xA4 0x68 0xC5 0xC7 0x4A

SW3(config)#do sh vtp status
[COLOR=#0000cd][B]VTP Version                     : running VTP1 (VTP2 capable)[/B]
[/COLOR]Configuration Revision          : 0
Maximum VLANs supported locally : 1005
Number of existing VLANs        : 16
[COLOR=#0000cd][B]VTP Operating Mode              : Transparent[/B]
[/COLOR]VTP Domain Name                 : CCIE
VTP Pruning Mode                : Disabled
[COLOR=#0000cd][B]VTP V2 Mode                     : Disabled[/B]
[/COLOR]VTP Traps Generation            : Disabled
MD5 digest                      : 0x23 0xE7 0x2E 0xA4 0x68 0xC5 0xC7 0x4A

Now if I change the VTP version from 1 to 2 on the server what will happen to SW2 and SW3?

SW1(config)#vtp version 2
SW1(config)#
SW1(config)#do sh vtp status
[B]VTP Version                     : running VTP2[/B]
Configuration Revision          : 1
Maximum VLANs supported locally : 1005
Number of existing VLANs        : 16
VTP Operating Mode              : Server
VTP Domain Name                 : CCIE
VTP Pruning Mode                : Disabled
[COLOR=#0000cd][B]VTP V2 Mode                     : Enabled[/B]
[/COLOR]VTP Traps Generation            : Disabled
MD5 digest                      : 0x60 0x31 0x32 0x77 0x21 0xD3 0xE1 0xEE

Now let's check SW2

SW2(config)#do sh vtp stat
[COLOR=#0000cd][B]VTP Version                     : running VTP2[/B]
[/COLOR]Configuration Revision          : 1
Maximum VLANs supported locally : 1005
Number of existing VLANs        : 16
VTP Operating Mode              : Client
VTP Domain Name                 : CCIE
VTP Pruning Mode                : Disabled
[COLOR=#0000cd][B]VTP V2 Mode                     : Enabled[/B]
[/COLOR]VTP Traps Generation            : Disabled
MD5 digest                      : 0x60 0x31 0x32 0x77 0x21 0xD3 0xE1 0xEE

Yup SW2 is now in VTP version 2 mode, what about SW3?

SW3(config)#do sh vtp stat
[COLOR=#0000cd][B]VTP Version                     : running VTP1 (VTP2 capable)[/B]
[/COLOR]Configuration Revision          : 0
Maximum VLANs supported locally : 1005
Number of existing VLANs        : 16
VTP Operating Mode              : Transparent
VTP Domain Name                 : CCIE
VTP Pruning Mode                : Disabled
[COLOR=#0000cd][B]VTP V2 Mode                     : Disabled[/B]
[/COLOR]VTP Traps Generation            : Disabled
MD5 digest                      : 0x23 0xE7 0x2E 0xA4 0x68 0xC5 0xC7 0x4A

NOPE!!!

So if there is a mismatch between the server and the client the server will upgrade the client from version 1 to 2. However your VTP transparent mode switches will not be changed by this since it's operating in transparent mode...

But, what if the client is in VTP version 2 and the server is in VTP version 1? Same thing, it will downgrade the client like this:

SW1(config)#vtp version 1


SW1(config)#do sh vtp stat
[COLOR=#0000ff][B]VTP Version                     : running VTP1 (VTP2 capable)[/B][/COLOR]
Configuration Revision          : 8
Maximum VLANs supported locally : 1005
Number of existing VLANs        : 16
VTP Operating Mode              : Server
VTP Domain Name                 : CCIE
VTP Pruning Mode                : Disabled
[COLOR=#0000cd][B]VTP V2 Mode                     : Disabled[/B][/COLOR]
VTP Traps Generation            : Disabled
MD5 digest                      : 0x65 0xA2 0xDA 0x2C 0x42 0xFA 0x48 0xA4

and on SW2

SW2#sh vtp stat             
[COLOR=#0000cd][B]VTP Version                     : running VTP1 (VTP2 capable)[/B]
[/COLOR]Configuration Revision          : 2
Maximum VLANs supported locally : 1005
Number of existing VLANs        : 16
VTP Operating Mode              : Client
VTP Domain Name                 : CCIE
VTP Pruning Mode                : Disabled
[COLOR=#0000cd][B]VTP V2 Mode                     : Disabled[/B]
[/COLOR]VTP Traps Generation            : Disabled
MD5 digest                      : 0xA8 0xD7 0xDB 0x13 0xE7 0x38 0x3A 0x7F

So there you have it, proof by IOS!

SubnetZero

vinbuck wrote: »

If the server is version 2 and the client is version 1, the server will bring the client up to version 2 automatically...just checked it on a pair of 3550s. Either way it seems that the client will match what the server is using and you can't change the version on the client side

Hey Vinbuck you're correct and I just wanted to help you prove your point!

Cheers!

vinbuck

SubnetZero wrote: »

Hey Vinbuck you're correct and I just wanted to help you prove your point!

Cheers!

Awesome....thanks for the in depth look. I hadn't even thought to put one of my switches in to transparent mode and see if the client tracked along with the VTP version changes. I've just gone through my first read of the SWITCH FLG and one round of labbing using the SWITCH lab manual so i'm trying to identify my weak areas now and drill down before I start taking Boson EX-SIM practice tests and begin my final review. Since the CCNP is so much more in depth than the CCNA and requires a longer timeframe to complete, i'm trying to really assess and refine my study habits as a preparatory step to starting on the CCIE track next year. Passing ROUTE really helped me put into perspective what Cisco is after for the NP level exams and how they like to extract the material out of you.

Did you find the CCNP a helpful step on the way to the CCIE?

SubnetZero

vinbuck wrote: »

Did you find the CCNP a helpful step on the way to the CCIE?

Absolutely!