Switches

[txrandom]

Do I have this right?

Let's say 2 hosts are connected to a switch and our on the same VLAN. The two hosts can communicate each other via just the switch. The frames don't travel all the way to the router, correct?

Let's say 2 hosts are connected to a switch but each our on separate VLANs. The switch will forward the frame to the router, the router back to the switch, and then the switch to the other host?


When a switch is filling out an ARP table it's only broadcasting on one VLAN. Does this mean a switch has an ARP table for each VLAN it's configured for?

 

[ScottMac]

You are correct.

At Layer two, two hosts on in teh same broadcast domain (VLAN) see and talk to each other directly (assuming all the addressing is correct).

If the hosts are on two different VLANs (broadcast domains), then the router (or, a routing process like in a Layer 3 switch) is required to pass the packets between the VLANs.

Individual tables are kept for each VLAN, otherwise a broadcast from one couldn't be distinguished from the others (they are all ff.ff.ff.ff.ff.ff) ... i.e., separate broadcast domains.

That is also, by the way, one of the evil things about running two address blocks in the same broadcast domain (like what Cisco calls a "secondary" address).

 

[txrandom]

Studying for the CCNA is complex... As soon as I read about something and begin to understand it, something else is added in to start the confusion all over.

 

[ScottMac]

Yessir, I agree. And THAT is exactly why it is very important to study and learn the fundamental knowledge (versus studying to pass a test).

If you take the time to understand the basic, foundational concepts now, learning the more complex concepts later is much easier. As an added benefit, if you truly understand the concepts, there is nothing they can throw at you on the test that you can't figure out without blowing a bunch of your time. Even if they change the test at the last moment, the concepts are always the same, and the test is no problem.

Study to learn, use the tests as a milestone to prove to yourself (and ultimately others) that you know what you're doing. You'll do much better at the tech interview too.

Good Luck