How can the communication from two different vlans of same segment can happen

[anirudh12b9]

Hi All,

Any one please resolve my query.

There are two vlans i.e vlan40&vlan50.I have two access switches in one switch i have configure vlan40 and i have assigned ip from range(192.168.10.1-192.168.10.10) to 10 desktops connected to 1st switch.

Know in another switch i have assigned vlan 50  and i have assigned ip from range (192.168.10.11 -192.168.10.20) to another 10 desktops.

And there is a trunk configured between these two access switches.And vlan 40 is not there in the access switch 2 and vlan 50 is not there in access switch 1.

My question is now how can these two pc's 192.168.10.2 & 192.168.11.3 will communicate without help of the L3 device i dont want use any any L3 device.

Please any body one provide the configaration for the same.

[InayathUlla Sharieff · Accepted solution]

Hi,

Let me see if I can put in simply words:-

1 - Scenario( Vlan 40 and Vlan 50 in same subnet)

PC1---Sw1---Trunk----Sw2---Pc2(Vlan50)

PC--Vlan 40 ( 192.168.10.1)

PC2- Vlan50 ( 192.168.10.2)

Trunk:- Now if you have configure the trunk between the two switches this will not work.

As you know when you configure the port as trunk port and the packet goes out of the port will have the vlan tag value added on top of it. Hence when the pc1 packets comes with Vlan 40 in its header and goes out of the trunk link of SW1 the vlan 40 will be added to the header hence when it reaches the SW2 it see were is the destination mac present , when it search it will not find any and it will not broadcast it bcz it doesn thave the vlan 40 in its database hence the packet will be dropped.

2- Scenario:-

 Vlan 40 and Vlan 50 in different subnet)

PC1---Sw1---Trunk----Sw2---Pc2(Vlan50)

PC--Vlan 40 ( 192.168.10.1)

PC2- Vlan50 ( 192.168.20.2)

This will also not work as you have different subnet present and without having layer 3 device in between vlan communication will not occur.

Solution:

========

1st scenario:- Make the port as access port connecting betwen the switches.( SW 1 trunk link will be no access port with vlan 40 on it. SW2 trunk link to conver to access port with vlan 50) this time it works.

2nd scenario- have layer 3 configuration on the svi it will work.

HTH

Regards

Inayath

*********Please do not forget to rate the post if this is helpfull **************

[Madhukrishnan Gopinathan Nair · Accepted solution]

I guess, Inaya has given you solution, but i like to add one more solution without changing trunk config between two switches.

On switch 1 trunk port, configure native vlan as 40, and on switch 2 port, configure native vlan as 50.

Hope this helps,

Thanks,

Madhu