Switching Problem - Picking Your Brain - Question Inside

streetking

So I came across this question when I was looking for practices before going in for my CCNA.
I am not quite understanding why host in VLAN1 would not be communicate with each other after the change.
802.1Q uses Vlan 1 as native Vlan by default. Fa0/1 on sw11 would send traffic to the other side untagged because it is an access link and it's sending native vlan (vlan1) traffic as configured by the technician per the question. On the other side of the link Fa0/1 on sw12 is a trunk port. As a trunk port, it forwards all frames based on its destination mac or floods out all port of the arriving frame's tagged vlan header. (as oppose to access port which forwards by configured vlan id). So Sw12 will still end up forwarding frames to hosts connected to the switch.

Sames goes the other way when traffic goes from sw12 to sw11. Frames leave Sw12 untagged which is native vlan1 default and arrive Sw11 as a vlan1 frame. So the answer should be A, "Only host in Vlan 1 can communicate with each other"

Please correct me if I am wrong.

EdTheLad

You would be correct if there were hosts in vlan 1. Vlan 1 is not being used, no access port associations and no additional info in the topology diagram. So therefore D is correct.

neno2014

I am still a student studying ccna but I would like to take a stab at this; fa0/1 on sw11 must be configured as a trunk port so that the vlans can communicate with there respective counterparts on sw12. For the vlans to communicate with each other they would need to be trunked to a a router.

As a student I would like to know if I am correct and if not why. This is so I can learn please.

EdTheLad

neno2014 wrote: »

As a student I would like to know if I am correct and if not why. This is so I can learn please.

You are incorrect, read my previous reply. Also read about how the native vlan on a trunk port works.

streetking

EdTheLad wrote: »

You would be correct if there were hosts in vlan 1. Vlan 1 is not being used, no access port associations and no additional info in the topology diagram. So therefore D is correct.

Thank you for your reply. What you said make sense.

The command however didn't show Fa17 and Fa23 so they are either an up/up or administratively shutdown trunk port. If they were plugged in with a host, the hosts between the 2 switches in Vlan1 would be able to communicate, right?

But then again, like you said, there are no additional info in the topology diagram.

EdTheLad

Ports fa17 and fa23 are obviously down, weather then are configured as access or trunks it doesn't matter, the output would be the same, if they were trunk ports up/up you would see them in the topology. If there were hosts in vlan 1 they would be able to communicate over the trunk using the native vlan as you previously mentioned.

Hondabuff

Been seeing a lot of posts with people posting **** site material lately.

clarson

neno2014 wrote: »

I am still a student studying ccna but I would like to take a stab at this; fa0/1 on sw11 must be configured as a trunk port so that the vlans can communicate with there respective counterparts on sw12. For the vlans to communicate with each other they would need to be trunked to a a router.

As a student I would like to know if I am correct and if not why. This is so I can learn please.

here are a few things to know,
1) any port on a switch can be configured as a trunk not just fa0/1
2) yes the switches need to be trunked for the different vlans to communicate (not really but it does save on interconnecting cables)
3) yes a router can be used for interVlan comunications
4) switches can be trunked to each other also (not needing a router)