native VLAN

Yes you are mixing things up. Native and default Vlan are not one in the same.

The security risk with Vlan 1 is that it is used by the switch by default for management traffic such as CDP, VTP etc. You do not want user traffic mixed in with these protocols. So it is best practice to not use Vlan1 and to prune it where not needed.

ok, but can you please help with other questions and explain the concept of native vlan?

What other questions? It sounds like you have the native Vlan concept down, its a Vlan that is not tagged on the trunk.

I think he means as far as changing it on the switch. Which you do using the native vlan command. This is what you are referring to correct?

Bl8ckr0uter

Remember: This must be the same on all switches or you will get an error basically stating that there is a native vlan mismatch.

knwminus wrote: »

Remember: This must be the same on all switches or you will get an error basically stating that there is a native vlan mismatch.

The native doesn't have to be the same on all your switches. It only has to be the same on both sides of a single trunk. You can easily have native 10 on one trunk and native 100 on another.

Networker is correct. Lab it out, you can see it for yourself. When you change it on the trunk link, if you wait you will get a message about native VLAN mis-match. Which goes away when configuring the other side of the trunk link to match the native VLAN. Then you could have the same switch have a trunk with a different native vlan to another switch.

I think I understand all that you said. But what is native vlan used for? And the frames on the native vlan are untagged...what frames? where do these frames come from? vlan 1? or that has nothing to do with vlan 1? I'm sorry if I can't ask a better question...

Actually... (from Lammle's book): "The trunk port is assigned a default port VLAN ID (PVID) for a VLAN that all untagged traffic will travel on."

so, what is the source of untagged traffic?

The source of the untagged traffic is what ever is sending traffic on that Vlan.

The native Vlan or PVID is just the Vlan that will not be tagged on the port. If the one side is static access to say Vlan 10 and your native is Vlan 10 then you can still have Vlan 10 communication.

newman555 wrote: »

I think I understand all that you said. But what is native vlan used for? And the frames on the native vlan are untagged...what frames? where do these frames come from? vlan 1? or that has nothing to do with vlan 1? I'm sorry if I can't ask a better question...

Actually... (from Lammle's book): "The trunk port is assigned a default port VLAN ID (PVID) for a VLAN that all untagged traffic will travel on."

so, what is the source of untagged traffic?

You definitely aren't understanding the concept of it. Dot1Q supports the use of a native vlan. By default that native vlan is vlan 1. You can change this to any vlan 1-4096, except for the reserved addresses 1002, 1003, 1004, and 1005. Also, 0 is reserved. With a native VLAN, the frames are untagged. That is how the switch distinguishes the native VLAN from any other VLAN that is configured with your network. The source of the untagged traffic, is frame that is sent from something assigned to that native VLAN. If you have a native VLAN of 5, but your hosts are on VLAN 3, then you won't have untagged traffic from those hosts, you will have tagged traffic with a ID for VLAN 3. It is always best practice to change the native vlan to a random vlan that isn't used, and do not make it the same as the VLAN that your hosts are on. You'll find out at a later time, if you advance to the CCNP studies why.

so...I put acces port fa0/1 in vlan 10. fa0/2 is my trunk port and I say that his native vlan is vlan 10. If I send anything from fa0/1 trough fa0/2 to the other side of trunk, it won't get tagged. right? that's it?

That is correct.

oooh...I think the whole problem in my head began when I read somewhere "native=default".

One last question...Where is this actually used? Example? Why would I make some vlan a native vlan? (ok, that's 3 questions...)

Thanks to everyone for explaining this, I really got stuck...