Two VTP Servers

[rob1456657]

Hopefully, I do not confuse anyone...

We have two locations, OLD Location has a 3750 Switch as the core and is a VTP Server, this core network has a few VLANs to it.

We have a new location that will eventually become the core of the entire network, this is a 9300 Switch. This switch also has a few VLANs and is the core of the new network. The IP Scopes between each core network is different so there is no issue there. However, we need to connect both the old network and the new network, and we are planning on having a 9200 that has a trunk to the 3750 and a trunk to the 9300. There is no routing protocol so we'll need to add static routes, for now, no biggie.

However, my question is, the 3750 and 9300 are both VTP Servers, when we marry the two networks via the 9200 will this cause any issues?

Should I be configuring the VTP servers in a specific way; for example, one as a client and leave the other as a server?

Need words of advice.

Thank you to anyone who responds. 

[marce1000]

 -            If the vtp-domains are currently different, there can be no 'initial conflict'

 M.

[rob1456657]

OK, that makes sense, but let me ask another question.

First here is what I have:

3750:

3750-CORE-SW#sho vtp status
VTP Version capable: 1 to 3
VTP version running: 1
VTP Domain Name: DOMAIN1
VTP Pruning Mode: Disabled
VTP Traps Generation: Enabled
Device ID: d6ae.8546.c151
Configuration last modified by 192.168.90.1 at 7-29-20 16:11:15
Local updater ID is 192.168.90.1 on interface Vl2 (lowest numbered VLAN interface found)

Feature VLAN:
--------------
VTP Operating Mode: Server

9300:

9300-CORE-SW#sho vtp status
VTP Version capable: 1 to 3
VTP version running: 1
VTP Domain Name: DOMAIN2
VTP Pruning Mode: Disabled
VTP Traps Generation: Disabled
Device ID: b08e.6f33.0b90
Configuration last modified by 10.100.1.1 at 7-22-21 14:20:19
Local updater ID is 10.100.1.1 on interface Vl100 (lowest numbered VLAN interface found)

Feature VLAN:
--------------
VTP Operating Mode: Server

Because the domains are different there should be no conflict? Correct?

What about the 9200 (this switch will have a trunk to the 3750 and a trunk to the 9300. This switch will inevitably be a VTP Client, what VLANs will it use? Or is my thinking on the wrong track?

[Joseph W. Doherty]

"Because the domains are different there should be no conflict? Correct?"

Yes.

BTW, with VTP versions 1 and 2, every VTP "client" is, "under the covers" also a "server".  What the "server" role permits is VLAN configuration changes on the device.  The real issues, with multiple servers, with these VTP versions, you can make VLAN changes on multiple servers at the same time, and since their revision numbers might be equal, VLAN database can now differ across multiple switches.

Also BTW, VTP version 3 has many more "rules" to protect the VLAN information.

"What about the 9200 (this switch will have a trunk to the 3750 and a trunk to the 9300. This switch will inevitably be a VTP Client, what VLANs will it use?"  Be careful, though, of adding it to the network with a default/null domain.

Depends what VTP domain it's part of. 

[rob1456657]

OK, this makes sense.

As for the 9200 switch, then I can add it to either the 3750 VTP Domain or the 9300 VTP Domain.

Or should I set the 9200 to transparent mode?

[Joseph W. Doherty]

"Or should I set the 9200 to transparent mode?"

That depends on a) you don't want that switch to "inherit" VTP VLAN info and, b), you want to relay VTP information through the switch.

If you don't want switch to use VTP VLAN info and relay VTP information, newer switches support another mode, "off".

[balaji.bandi]

Easy and quick way  i can think do not like any complicated, If you do not need any Layer 2 extenstion between these switch.,

I run P2P Layer 3 Link between 2 ( 9300 and 3750) 9200 still act as Layer 2 Trunk  with VTP Transparent. use different VLAN number which is not part of your network (for unique).

If you looking Layer 2 required to extend both sides, is the VTP Domain and VTP Versiion same both the sides ?

[Giuseppe Larosa]

Hello @rob1456657 ,

>> There is no routing protocol so we'll need to add static routes, for now, no biggie

I agree with @balaji.bandi if all you need is a L3 connection between the two sites you can use a L3 routed p2p link.

if you want to extend some VLANs between the two sites it is a different matter and the L2 trunk with selected VLANs allowed over it is the easiest solution.

if you have a device in the middle a Cat9200 remember that DTP does not allow a trunk to form when there is a VTP domain name mismatch so you need to use

switchport mode trunk

swwitchport trunk allowed vlan X1,X2,X3

Hope to help

Giuseppe

[rob1456657]

Ok, with what you just mentioned here is where I am at with this configuration.

The new 9200 switch is in place, but I added it to the 3750 VTP Domain because I needed those VLANs to be available on the 9200. I wanted to make sure that adding this new 9200 did not bring down this section of the building because it runs some large cranes for product picking.

That part is all good!

The 3750 is a VTP Server - Domain Domain1.

The 9200 is a VTP Client in VTP Domain Domain1.

All VLANs are working on the 9200.

Now, the new building is the one that has a 9300, that's a different domain VTP Domain2. 

The plan is to configure a trunk to the 9300 so that we can access both sides.

If I understand this correctly, the trunk needs to specifically allow VLANs through. From both sides?

For example, If I configure the trunk on the 9200, do I need to switchport trunk allow vlan v1,v2, v3, and then on the 9300 do the same thing but for the VLANs I want to allow from that side? 

Thanks, everyone for the assistance.

[Joseph W. Doherty]

By default (or so it has been in the past), all VLANs are allowed on trunks.  Defining what VLANs are allowed on a trunk should only be needed if you wish to limit the trunk to a subset of your VLANs.

[rob1456657]

OK, do you think there will be any issue with adding a trunk from the 9200 (VTP Domain Domain1) to the 9300 (VTP Domain Domain2)?

Basically, the setup will look like this:

3750 (VTP Domain1)--TRUNK-->9200(VTP Domain1)<--TRUNK--9300(VTP Domain2)

The VLANs on the 3750 are different from the 9300, but we need to be able to access both sides of the network via the 9200.

I have folks (offline) that say I might have issues. This is why I am posing this question here to gather more experienced answers.

Thanks, everyone for the assistance.

[Joseph W. Doherty]

"I have folks (offline) that say I might have issues."

Yes you might.  VLANs will transverse the trunks and 9200 will only learn VLANs from domain its part of.

So, what kind of problems might you have?  They would be related to mismatched VLANs.

Say in domain 1 you have VLANs 1,2,4 and in domain 2 VLANs 1,3,4.

VLANs 1 and 4 will carry all their VLAN traffic across both domains (I'm assuming we're not blocking VLANs on the trunks).

9300 will, by default, will forward VLAN 2 to 9300, but 9300 doesn't know of it.  Conversely, by default, 9300 will forward VLAN 3 to 9200 but 9200 doesn't know of it either.  Depending where you want those VLAN this could be an issue.

[rob1456657]

That makes sense.

Ultimately, the 9300 is going to be the core of the entire network. But for now, I need to make sure we can access everything.

Here are our VLANs:

3750:

VLAN4

VLAN7

VLAN50

9300: 

VLAN601

VLAN602

VLAN603

Based on the VLAN information we know, what's the best course of action?

[Joseph W. Doherty · Accepted solution]

Best course of action depends on what VLANs you want your 9200 to know.

If all, you can set VTP mode to off and define all of them on the 9200.

Otherwise, also for all, you can define one domain's VLAN, known on the 9200 to the other domain, and optional the converse too.  The former would have all the VLANs known to the 9200 via VTP, and all the VLANs known to the domain that the 9200 isn't part of.  The latter, insures all the VLANs are known to both domains.

[rob1456657]

Hoping someone can provide some clarity here.

OK, so here is where I am at with this configuration.

• 3750 – VTP Server (VLANs 4, 7, and 50) – VTP Domain (MDC)
• 9200 – VTP Client (VLANs 4, 7, and 50) – VTP Domain (MDC)
• 9300 – VTP Server (VLANS 601-603) – VTP Domain (NEWMDC)

I manually added the VLANS from each side to the other side, so basically, both VTP Servers have VLANs 4, 7, 50, and 601-603.

I have a fiber connection between the 9200 and 9300 which is a trunk. I successfully configured a port on the 9200 for VLAN 603 and the client connected to that port got a DHCP IP from the DHCP server on VLAN 603.

When I check the mac address-table on bot the 9200 and 9300 I can see devices in all the VLANs, and CDP Neighbors shows me the switches on either side.

However, my problem is the 3750 is the router for our original network, the 9300 is the router for the new network. If I add a static route for the interface on VLAN601 on the 3750 it does not work ( I am unable to ping), and vice versa on the 9300.

Examples:

3750 -

ip route 10.60.1.0 255.255.255.0 192.168.50.2 (This is the 9200 with the fiber connection)

9300 -

ip route 192.168.50.0 255.255.255.0 192.168.50.2 (This is the 9200 with the fiber connection)

I also attempted to point the subnet to the VLAN interface on either side. (i.e., 10.60.1.1 or 192.168.50.1)

Is this incorrect, or how should I go about this?