Configure two VTP domains: Domain VTP1, from which DLS1 is the server and domain VTP2, from which DLS2 is the server

[Maxim Sevostyanov]

Hello All,

Four switches as shown below

DLS1=====DLS2

   ||                 ||

ALS1           ALS2

Also connection between DLS1 == ALS2 and DLS2 == ALS1

These domains have the following characteristics: in both domains, all other switches are clients.

Domain VTP1 will serve VLAN 10 and Domain VTP2 will serve VLAN 20

How is possible to configure the same switch to be a server for one domain and client for another.

Thank you for any advise.

[omz]

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@Maxim Sevostyanov wrote:

How is possible to configure the same switch to be a server for one domain and client for another.

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Hi 

I don't think it is possible to configure multiple domains on the same switch and have the switch as a server in one domain and client on the other.

I have not read or come across this sort of requirement. 

Let's see what others have to say .. 

[paul driver]

Hello

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@Maxim Sevostyanov wrote:

How is possible to configure the same switch to be a server for one domain and client for another.

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It isn't possible to have the device running in two vtp domains

[Maxim Sevostyanov]

Thank you for your replay. I thinking the same as you but this is a real task from a tutor. I found similar thread https://learningnetwork.cisco.com/thread/4333?start=0&tstart=0 , and answer were "So if you want to have two (or more) VTP domains, then the switches for each domain will have to be contiguously inter-connected" I have no idea how to setup it.

[Giuseppe Larosa]

Hello diamonduk,

a single switch can be a member of only one VTP domain.

However, switches belonging to different VTP domains can be interconnected using a trunk port.

The switches need to use the command

switchport mode trunk

and eventually

switchport nonegotiate

The reason is that DTP messages carry the VTP domain info inside and does not allow a dynamic trunk to be formed so switchport mode desirable cannot be used to achieve a working trunk link between two VTP domains.

This is probably the objective of the exercise.

Of course the trunk link makes sense only if the two VTP domains share at least one Vlan in their own separate Vlan databases.

The trunk link should allow all the Vlans in common between the two VTP domains (Vlans present in both VTP Vlan databases).

if no Vlan is present in both VTP domains  a L2 link makes no sense unless using two access ports to join Vlan X in VTP1 with Vlan y in VTP domain 2 but this can be considered not best practice in real world.

Hope to help

Giuseppe

[Joseph W. Doherty]

As the others have explained, we don't believe it's possible for a switch to participate in more than one VTP domain, however as Giuseppe explains switches in different VTP domains can pass traffic on "shared" VLANs (just, again, they won't share VLAN information between VTP domains).

If this is a "real task" from a tutor, have them clarify what exactly they hope to achieve.

NB: it's certainly possible you can manually "toggle" a switch between VTP domains, i.e. have its VLAN database change, on-the-fly, depending on which VTP domain it's part of at that time.

[Maxim Sevostyanov]

Thank you so much, everyone, who read and replied.

Yes, I understood, It is possible to communicate between two different VTP domains, but not as VTP domains as @Joseph W. Doherty mentioned they won't share VLAN information between VTP domains. Different VTP domains can communicate as a different network, by just route the packets to other VTP network.

I know and another member of the community confirmed about VLAN synch between 2 different VTP domains NO that's not possible.

A tutor replay: There is nothing muddled - this can be done. 

Think beyond the text and think about what is being asked for - this is a question that recurs every presentation. There is a level of challenge and exploration here.

I think I will configure VTP1 domain first, then configure VTP2 (by destroying VTP1) because in a question probably says configure two domains but not the same time.

Interesting idea from @Joseph W. Doherty about "toggle" as switch between VTP domains, I think there are some tclsh skills required. 

Again, thank you so much, everyone. 

[Giuseppe Larosa]

Hello Norman,

when you will change the VTP domain on the switch you will find out that the Vlan database is replaced with the Vlan database of VTP domain2.

It is not clear what your tutor would like you to do.

Keep use informed on what is the tutor's solution for this exercise.

L2 communication between two VTP domains on "shared" Vlans is possible on a trunk link.

Changing the configuration in a switch to be first in VTP domain1 and then in VTP domain2 makes no sense in real world networking as the final result should be like configuring it for VTP domain 2 from the beginning.

Hope to help

Giuseppe

[Maxim Sevostyanov]

Thank you, @Giuseppe Larosa 

Yep, as you say configure VTP1 than VTP2 equal to configure VTP2 from the beginning. 

I will keep posted if a tutor gives more info or final solution. 

Can we assign VTP domain for ports? I think if we create SVIs on all switches than create VTPs domains for each network (with SVIs) than we can interconnect them.

[Giuseppe Larosa]

Hello Norman,

>> Can we assign VTP domain for ports? I think if we create SVIs on all switches than create VTPs domains for each network (with SVIs) than we can interconnect them.

VTP can be configured only in global mode at node level.

In addition to this VTP is a L2 control protocol and SVIs are logical L3 interfaces.

VTP uses the IP address of an SVI  (if I correctly remember the lowest number SVI that is up and configured with an IP address) only to provide an easy to read info about the identity of the last updater of the VTP database (last VTP server that made a change)

But VTP messages are not carried within IP packets they are L2 frames with a specific encapsulation and using a specific L2 multicast MAC address

Edit.

for more details about Cisco L2 protocols see this old but useful doc

https://content.cisco.com/chapter.sjs?uri=/searchable/chapterhttps://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6500/ios/12-2SX/best/practices/recommendations.html.xml&searchurl=https%3A%2F%2Fsearch.cisco.com%2Fsearch%3Flocale%3DenUS%26query%...

Well actually the document in the past provided the encapsulation and multicast addresses used by Cisco protocols like VTP, CDP, DTP, PVST.

Hope to help

Giuseppe

[Maxim Sevostyanov]

Thank you, @Giuseppe Larosa for link and explanation. 

In my assessment, I will describe impossibility create TWO VTP domains.

Also, I will do one VTP domain with two switches in vtp mode server (DLS1 and DLS2)

• add VLAN 10 on the left server (SW: DLS1)
• add VLAN 20 on the right server (SW: DLS2)
• Switches ALS1 and ALS2 vtp mode client
• The result would be all switches will get VLAN 10 and 20;

At least something.

[jzzzzzzz]

Did you ever figure out what they were really looking for? Pretty sure I've got the same question!

[Maxim Sevostyanov]

Hello, there,

Thank you for coming back to this question, as I sent my answers to tutor without the answer.

I have got an answer like this place switch into transparent mode and create VLANs as many as you want manually because "the ground rule says you can have only one VTP domain name configured in a switch"

Really thank you so much for everyone who replied on this topic.

Stay Safe.

[Vishnu Vardhan S]

The ground rule says you can have only one VTP domain name configured in a switch. Answer for that question is No . 

I believe your tutor is trying to playing with the question he is giving to you. 

If that statement is true then we can configure 10 ip address in a single L3 interface its just that every time you type new ip address the older one will get replaced. 

Please let us know why you want like that.