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Talk between 2 VTP domain

Hi,

How to make 2 different VTP domain talk to each other .Both domain are in same building .

Thanks

CD

22 REPLIES

Re: Talk between 2 VTP domain

Hi CD,

2 different VTP domain will never talk to each other.

Yes if the switches in 2 different buildings are with same VTP domain name and password then if you have a trunk between the 2 switches they will talk to each other.

But 2 swithches with 2 different domain name will never talk to each other.

HTH, if yes please rate the post.

Ankur

Re: Talk between 2 VTP domain

Hi CD,

Are the vlans same on both the domains. Lets us say if you have 2 doamins VTPA and VTPB.

If you want to join both of them, you change the domain name to VTPA on the server in VTPB domain and then uplink via trunk to the switch in VTPA domain. make sure that its revision number is less than or equal to the server in VTPA. Then change the domain name on all the client switches in VTPB to the one in VTPA.

You can keep the 2 VTP servers in your n/w for redundency if in case one goes out the vlan info should be kept same across the VTP domain.

HTH, Please rate if it does.

-amit singh

New Member

Re: Talk between 2 VTP domain

Hi ,

Actualy i was discussing this thing with my friend and this question arises.Lets say VLANS are different on both the domain and i want to keep those domain name , then there is no way that 2 domain can talk to each other ?

regards

CD

Re: Talk between 2 VTP domain

CD,

If you have 2 diff domain names, they cannot talk to each other.

If you have diff vlans and you want to merge the domains then, the moment you change the domain name on the switches, it will join the domain that one you want.

HTH, Pls rate if it does.

-amit singh

Re: Talk between 2 VTP domain

Hi CD,

No there is no way 2 different domains can talk to each other.

HTH

Ankur

New Member

Re: Talk between 2 VTP domain

If I have two VTP domains in two diff buildings, and a adding a L3 device in between, will the devices talk to each other?

SS

Re: Talk between 2 VTP domain

Hi Satya,

It is 2 different VTP domain and not 2 different subnets so layer 3 device in between does not matter. If you have 2 different VTP domains switch will still talk to each other , data will still pass and will have no affect only vlan info will not synch.

VTP request are always multicast and remain on layer 2.

You have to have a same VTP domain if you want VLAN info to synch.

HTH, if yes please rate the post,

Ankur

New Member

Re: Talk between 2 VTP domain

Hi ,

I would like to know how to connect these 2 different VTP domains so that users on VTP_Domain_A can talk to users of VTP_Domain_B ? by trunking ?

regards

Neo

New Member

Re: Talk between 2 VTP domain

To my knowledge the two devices may be able to communicate, but NO VLAN information will be sync'd with the two separate VLANs.

You must join one switch or the other to the same VTP Domain name for the VLAN info to be sync'd.

New Member

Re: Talk between 2 VTP domain

Hi ,

I would like to know how to connect these 2 different VTP domains so that users on VTP_Domain_A can talk to users of VTP_Domain_B ? by trunking ?

regards

Neo

New Member

Re: Talk between 2 VTP domain

hi,

Please help....

regards

Neo

Re: Talk between 2 VTP domain

Neo,

You will be able to talk between the Vlans in diff VTP doamin but the VLAN info will not get syncd. You need a layer 3 device to do the routing. If you have a layer 3 switch then you can connect all of the switches via trunk and have it do your intervlan routing. You can also use a router and do a router on stick config.

HTH, Please rate if it does.

-amit singh

New Member

Re: Talk between 2 VTP domain

Hi Amit ,

thanks for the info.I am aware that VLAN info will not synch between two diff VTP domains what i would like to know is ,say User A is there in VLAN_13 in VTP_Domain_A and user B in VLAN_13 in VTP_Domain_B .If we enable Trunk between two switches how do switch will know that particular User datais for UserB is in other domain ? If u have any link on this , please provide me that .

regards

Neo

Re: Talk between 2 VTP domain

Neo,

When you are trunking 2 switches, you are just extending your Vlans on the network.On Layer2 switch User A in VTP_Domain_A and user B in VLAN_13 are the part of the same Vlan. For example When user a wants to ping the user B first it will send an arp request.. that arp broadcast will travel via trunk to another switch and when the userB sends the arp reply that MAC will be leraned on the trunk port and will be a part of Vlan 13. This is how the communication will occur.

If the users are in diff vlan, that's where the L3 funcationality comes into the picture.

Now if we talk about VTP, as the domain names are diff, their Vlan databases will not get syncd.

HTH, Please rate if it does.

-amit singh

Re: Talk between 2 VTP domain

Hi Neo,

VTP domain is not at all concerned with communication between same vlans on multiple switches.

VTP as you know is just to get rid of manual vlan creation on multiple switches in big network.

But if you aready have vlan created like vlan 13 on switch with VTP Domain A and on switch with VTP domain B they can talk to each other if you have trunk between the 2 switches or even if you have an access port between 2 switches but the access port is configured for vlan 13.

Now because User A and User B are in same vlan they are in same broadcast domain so they do not need any layer 3 device and mac address of user B will be learned on switch who is in VTP domain A via trunk port and now when User A waan a talk to User B on other switch the frame will have the destination mac address of user B and when the farme from user A will enter switch which is in vtp domain A it will know that it has to move out of trunk port where the mac address is leraned and in this way it will reach switch who is in vtp domain B and vice versa will happen.

Hope I am clear with my explaination.

Pleas rate the post if it helped.

Regards,

Ankur

New Member

Re: Talk between 2 VTP domain

Hi Ankur !,

Thanks for your long reply.Now my next question is just guess that already VLAN_13 (10.X.X.X)is created in my VTP_Domain_A and now if VTP_Domain_B comes in picture with same name VLAN_13 (192.168.X.X) ? now how the VLAN info will be tagged ?

regards

Neo

Re: Talk between 2 VTP domain

Hi Neo,

Now here is the trick, VLAN info will be tagged the same way because on top of IP packet there is always a layer 2 frame encapsulation so no matter whatever IP you give to machines vlan information will be tagged the same way on trunk.

But because the 2 machines are on different network they will not talk to each other on layer 3 but yes layer 2 communication will work fine by which I mean machine B will reply to machine A for layer 2 broadcats ARP request. But if you try to ping machine B from machine A you will not get a reply because they are in different network.

HTH, if yes please rate the post.

Ankur

New Member

Re: Talk between 2 VTP domain

Hi Ankur,

AFAIK VLANs are created when a single broadcast is broken into multiple broadcast domain .So how will ARP will get the reply if these 2 machines are in different broadcast domain or You mean to say , as the name of the VLAN is same broadcast will travel from User_A which is in VLAN_13 on VTP_Domain_A to User_B which is in VLAN_13 on VTP_Domain_B , considering the fact ip addressing of both the VLANs are different ?

regards

Neo

New Member

Re: Talk between 2 VTP domain

Hi,

any thoughts...

regards

Neo

Re: Talk between 2 VTP domain

Hi Neo,

Considering the fact machine B and machine A has different ip address but still they are in same vlan.

Any layer 2 broadcast will reach machine B as when any traffic move out from machine A on switch A and hits the interface it will get a PVID of vlan 13 and it will broadcast the ARP request to all the ports in VLAN 13 which will also reach machine B because it is also in vlan 13 on switch B.

But when machine A will try to ping then it will check the boolean algorithem and will come to know machine b is in different network and will not get a reply.

HTH, if yes please rate the post.

Ankur

Re: Talk between 2 VTP domain

hello Mr. Ankur,

now here as we are talking about different IP address right??? now is it possible to establish communication using any layer 3 functionality...

regards

Devang

Silver

Re: Talk between 2 VTP domain

With the VTP domain issue pushed aside for now. to make the VLAN subnet communicate via a trunk . This will work if you use Dot1Q trunking and set the Vlans in question to the native vlan's. Dot1Q will not tag the native VLAN. so if you have say vlan 1 on one switch set for native and the other switch is set for vlan 10 as native. If you Dot1Q trunk between them the VLAN subnet will communicate.Do not allow other VLAN's to go across the trunk.Since your VTP domain are not sync'd you will see different subnets on any similiar VLAN's numbers....Hope this helps....

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