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Two networks on Same VLANID on two switches

I have a question regarding vlans. If I ahve two switches A and B and a Router RA. If switchA has two VLAN 1 and 2, and swB has one vlan 1. Does the network have to be the same on both VLAN 1? swA VLAN 1 is a.b.c.d, vlan2 is network w.x.y.z. If swb vlan1 is network w.x.y.z could have a trunk between these two switches and the router so that bot networks can communicate with eachother or do I have to move each respective vlan to match the netowork on each switch.

1 ACCEPTED SOLUTION

Accepted Solutions

Re: Two networks on Same VLANID on two switches

Hello,

Set all the ports on network y.y.y.y to vlan 2 and set your trunk port normally so that vlan 1 is on it since your vtp traffic uses the native vlan to communicate.

Example

SWITCH A

vlan database

vtp domain cisco

vtp mode server

exit

interface fa0/1

Description ***Connected to router***

switchport trunk encapsulation dot1q

switchport mode trunk

interface fa0/2

Description ***Connected to Switch B***

switchport trunk encapsulation dot1q

switchport mode trunk

SWITCH B

vlan database

vtp mode client

vtp domain cisco

exit

interface fa0/1

Description ***Connected to Switch A

switchport trunk encapsulation dot1q

switchport mode trunk

interface fa0/2

Description ***Set all y.y.y.y interfaces to vlan2***

switchport mode access vlan 2

Patrick

HTH please rate any posts that are helpful.

5 REPLIES

Re: Two networks on Same VLANID on two switches

Hello,

Let me make sure I have your topolgy right.

RTRA trunks to Switch A that has VLAN 1 and VLAN 2 then Switch A connects to Switch B that has VLAN1

Switch A vlan 1 is network x.x.x.x

Switch A vlan 2 is network y.y.y.y

Switch B vlan 1 is network y.y.y.y

The only way I can think to make this work is to set the port connecting Switch A to Switch B in access mode for vlan 2 while switch B's port connecting to switch a is in access mode for vlan 1.

For best practice I would recommend you trunk between the switches in the future and reassign Switch B ports to vlan 2.

Patrick

HTH please rate any posts that are useful.

New Member

Re: Two networks on Same VLANID on two switches

I agree that is the best design. So then on Switch B do I have to reassign the native VLAN as well or could I just make all the ports in access mode to VLAN 2 and not worry about the native VLAN which is VLAN 1 by default.

Re: Two networks on Same VLANID on two switches

Hello,

Set all the ports on network y.y.y.y to vlan 2 and set your trunk port normally so that vlan 1 is on it since your vtp traffic uses the native vlan to communicate.

Example

SWITCH A

vlan database

vtp domain cisco

vtp mode server

exit

interface fa0/1

Description ***Connected to router***

switchport trunk encapsulation dot1q

switchport mode trunk

interface fa0/2

Description ***Connected to Switch B***

switchport trunk encapsulation dot1q

switchport mode trunk

SWITCH B

vlan database

vtp mode client

vtp domain cisco

exit

interface fa0/1

Description ***Connected to Switch A

switchport trunk encapsulation dot1q

switchport mode trunk

interface fa0/2

Description ***Set all y.y.y.y interfaces to vlan2***

switchport mode access vlan 2

Patrick

HTH please rate any posts that are helpful.

New Member

Re: Two networks on Same VLANID on two switches

Thanks that resolved it.

Re: Two networks on Same VLANID on two switches

No problem if you have any other questions just ask.

Patrick

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