Actually, in a production network with many vlans, I think there will be
more traffic on the trunks. If one port is a trunk and it has 5 vlans
configured, a broadcast from all vlans will traverse the trunk - so if all
vlan's broadcast at the same time, instead of 1 broadcast - as most ports
will see - the trunk will see 5.
As far as traffic passing the trunk where it is not destined for a user on
that trunk...Only broadcasts, multicasts, and unicasts destined for a real
user will traverse the trunk. So a unicast to a user off swich C will not
be seen by switch B. On switch A, if you do a "sh cam dynamic" you will see
MAC address mappings to the trunk port interface of users off switch C.
If you start talking about multiple VLANs then you can look at VTP prunning.
If setup properly, it will only send traffic on a trunk if there is a
particluar VLAN configured on a switch off that trunk. In your scenario,
say you have 3 VLANs. VLAN 1 is configured on all 3 switches. VLAN 2 is
only on switch C and A. VLAN 3 is only on Switch B and A. Switches B and C
are trunking to switch A. Switch A has user ports in all 3 VLANs. A
broadcast from a port on switch A in VLAN 2 will not traverse the trunk to
switch B, because there are no user ports in that VLAN anyway. Makes sense
huh?
Kenny
----- Original Message -----
From: "Gerwin Boschloo" <[EMAIL PROTECTED]>
To: "'Shaq Patel'" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
Sent: Sunday, June 04, 2000 2:58 PM
Subject: RE: VLAN Trunk traffic question
> I don't think so. A trunk type is just a tag type and has nothing to do
with
> the traffic inside it. When you configure VLAN's, you split up your
network
> into broadcast domains. So I think that you will have less traffic on a
> trunk than you have without the trunks. Beware that when you (in the
router)
> bridge between the VLAN's, the amount of traffic will be increased because
a
> broadcast on VLAN 1 will also appear in VLAN 2.....so this broadcast will
be
> twice inside the trunk.
>
> I hope this helps,
>
> Gerwin
>
> -----Original Message-----
> From: Shaq Patel [mailto:[EMAIL PROTECTED]]
> Sent: Friday, June 02, 2000 1:08 AM
> To: [EMAIL PROTECTED]
> Subject: Re: VLAN Trunk traffic question
>
>
> ISL and done deal-
>
> John Neiberger wrote:
>
> > Ok, I'm suffering from a brain cloud at the moment. So, willing to
suffer
> > the comic flames and arrows, I ask the following question:
> >
> > Assume we have three switches: A, B, and C. A has a fast ethernet
> > connection to B and another to C. B and C are not directly connected.
At
> > this point, these are not trunk lines and they are in the same VLAN.
That
> > means only traffic destined for B goes down the line to B, and traffic
> > destined for C goes to C.
> >
> > Now, if I were to make both of those connections trunk lines, either ISL
> or
> > 802.1q, would I still have only B-destined traffic going to B or would
> that
> > trunk be passing all traffic for that entire VLAN up to B even though
> > C-destined traffic is a waste of bandwidth on the B trunk?
> >
> > Thanks for the help, as always!
> >
> > _______________________________________________________
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