Question regarding VLANs

[chandra_rc16]

Hi All,

I'm practicing VLANs for my CCNA and i just got a weird doubt.

My understanding:

By default all the ports of a switch will be in VLAN1. And Access ports doesn't tag any VLAN information, only trunk ports tag VLAN information.;

So if i connect a PC1 to switch0 on its Fa0/10 port, by default PC1 will be in VLAN1

Similarly if i connect a PC2 to a switch0 on its Fa0/20 port (configured to be in VLAN2) PC2 will be in VLAN2.

Likewise if i connect a switch1 to switch0 on Fa0/11 port (This port is in VLAN1) then from the switch0's perspective switch1 is in VLAN1.

So the VLAN1 devices on the switches will be able to communicate properly.

Question:

If i move the port on switch1 which is connected to the Fa0/11 port (in VLAN1) of switch0 to be in VLAN2, then what will happen ?

Will switch0 forward the traffic of VLAN1 on its Fa0/11 port towards switch0's port , if so will switch1's port will accept it /decline it ?

Thanks in advance. Please don't mind if the question seems to be silly.

Regards,

Chandu

[Jon Marshall]

Chandu

If i move the port on switch1 which is connected to the Fa0/11 port (in VLAN1) of switch0 to be in VLAN2, then what will happen ?

Will switch0 forward the traffic of VLAN1 on its Fa0/11 port towards switch0's port , if so will switch1's port will accept it /decline it ?

No it will not forward traffic for vlan 1 it will only forward traffic for vlan 2. If you want the link to forward traffic for both it needs to be a trunk link. An access port only carries traffic for one vlan and that vlan is untagged.

Jon

[chandra_rc16]

Sorry here the questin is : A typo mistake.

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Will switch0 forward the traffic of VLAN1 on its Fa0/11 port towards  switch1s port , if so will switch1's port will accept it /decline it ?

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Regards,

Chandu

[Jon Marshall]

Chandu

Still no. If the port is in vlan 2 then the switch will not forward vlan 1 frames down that link.

Jon

[chandra_rc16]

Switch0 (Fa0/11) in VLAN1 -----> Switch1 (Fa0/11) in VLAN1...  then devices on both the switches in VLAN1 will communicate.

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Switch0 (Fa0/11) in VLAN1 -------> Switch1 (Fa0/11) in VLAN2... Then what ?

Question:

The VLAN1 Broadcast/multicast frames will also be received by Fa0/11 port on switch0 because it is configured to be in VLAN1. So the Fa0/11 port on switch1 will see that frame.

Question:

Why don't switch1 takes that frame as a vlan2 frame and flood it for all the ports in VLAN2 on switch1.

Regards,

Chandu

[venkateshwarlut]

Hi Chandra,

                  Yes Chandra, Switch1 will takes that frames as VLAN 2 and flood to VLAN 2 devices.

So now communication as below

VLAN 1 devices in SWITCH0 will communicate with VLAN 2 devices in SWITCH1 and vice versa.

VLAN 1 devices in SWITCH0 will not communicate with VLAN 1 devices in SWITCH1 and vice versa.

Thanks

Venkat

[chandra_rc16]

Theoritically this is correct.

But if i want to see it practially, is there any way.

FYI: I don't have a real equipment. I'm practicing for my CCNA with the help of PT.

Regards,

Chandu

[chandra_rc16]

Any update ?

Regards,

Chandu

[chandra_rc16]

Theoritically this is correct.

But if i want to see it practially, is there any way.

FYI: I don't have a real equipment. I'm practicing for my CCNA with the help of PT.