transparent switch...what's the point?

Ok, this is kind of a continuation from my other thread regarding VLAN's but I figured I'd start a new fresh one with a little more info....

My setup is this:

server--->transparent--->client

So here's the jist of what I'm seeing. (no VTP pruning)

If I have VLAN 100 on the server switch. Hosts cannot ping each other that are on server and client UNLESS the transparent switch has that particular VLAN created. If it's created, hosts can communicate with each other.

I know in my other thread, I was told not to mix and match transparent switches with server/client switches.

So here's my question.

What is the point of transparent bridges then if the only point is to serve local VLAN use? Why call it transparent mode. Isn't that a little misleading? Shouldn't it be called local mode?

But I'm not here to argue the naming convention.

What I'm confused about is that transparent will share VTP info to clients but that's it. So to me, it seems misleading.

What is the point of sharing VTP info to client switches if they can't access hosts on other switches UNLESS that particular transparent switch has that VLAN configured. And that goes against the whole point of using VTP to automate and make administration easier...

Sorry for the rambling, I'm just trying to get my thoughts out.

Can someone help me understand what purpose switches in transparent mode serve, sitting in between a server and client switch? (other than sharing useless VTP info)

server--->transparent--->client

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Comments

mikej412

They are transparent to the VTP Advertisements -- they ignore them but pass them along.

As long as you don't enable pruning (or make sure the VTP Domain VLANs in use do exist on the transparent mode switch) the switch in VTP Transparent mode should be "transparent" to the Server and Client switches.

notgoing2fail wrote: »

Can someone help me understand what purpose switches in transparent mode serve, sitting in between a server and client switch? (other than sharing useless VTP info)

server--->transparent--->client

There isn't any -- that why you don't mix 'n match Transparent mode switches in with Server/Clients. And if for some reason you do -- like being a CCNA noob -- then you may learn the hard way not to enable pruning.

notgoing2fail

mikej412 wrote: »

They are transparent to the VTP Advertisements -- they ignore them but pass them along.

As long as you don't enable pruning (or make sure the VTP Domain VLANs in use do exist on the transparent mode switch) the switch in VTP Transparent mode should be "transparent" to the Server and Client switches.

Yeah all switches belong to the same domain. I'm just not understanding why the client switch would care about knowing what VLAN's exist if it cannot communicate with other hosts on other switches unless the transparent switch also has those VLAN's created on itself?

Again, I now know that mixing transparent/server and client is a no no for the most part, I'd like to know if I'm missing the bigger picture about transparent mode unless that's pretty much all there is to it?

And for those in charge of production networks, if there's ever a case where you would want to have transparent bridge between your server and client switches?

notgoing2fail

mikej412 wrote: »

There isn't any -- that why you don't mix 'n match Transparent mode switches in with Server/Clients. And if for some reason you do -- like being a CCNA noob -- then you may learn the hard way not to enable pruning.

Thanks. I caught this just after I made my last post.

So it almost seems more of a lab purpose kinda deal and just something theoretical from the CCNA learning standpoint but nothing that would ever be implemented in production. But now I know....

mikej412

The transparent mode switch doesn't know or care about the VLANs on the other switches. When you enable pruning -- if it doesn't have VLAN 88, it doesn't care about VLAN 88 and VLAN 88 may get pruned between the VTP Server switch and VTP Transparent switch -- which leaves the hosts in VLAN 88 hanging off the VTP Client switch cut off from the hosts in VTP 88 attached to the VTP Server switch.

If you manually create VLAN 88 (and probably make it active) on the Transparent switch -- then it won't get pruned off the trunk between the VTP Server Switch and VTP Client switch -- and all if fine.

Or as stated -- if you don't prune, then all the traffic gets sent through all the trunks and you don't see the problem.

notgoing2fail

mikej412 wrote: »

Or as stated -- if you don't prune, then all the traffic gets sent through all the trunks and you don't see the problem.

No wait, I wasn't pruning at all. It was disabled. So are you saying that with NO pruning, all traffic should get sent through the trunk between the server/transparent, and then from transparent/client?

I understand the transparent mode switch doesn't care about any vlan's on the server switch, I always thought though that the trunking interface would still carry the tagged vlan traffic through the transparent switch and onto the client switch...

So let's take pruning out of the equation. Hosts on switch A SHOULD be able to communicate with Switch C through Switch B ?