OT: Looking for a Cisco person.

[Bill McGonigle]

On Mar 15, 2005, at 14:23, Travis Roy wrote:

> Please let me know if this makes sense.
>
> Not all customer on the switch are on a vlan. So customers not on a 
> vlan are dumping traffic onto customers with a vlan via the trunk port 
> (to the router).

Maybe it makes sense and I'm missing something.

Why would the customer ports be specified as VLAN trunk ports?  That's 
not how you'd typically set it up.

Look for an interface that looks like this (snipped from one of my 
switch configs):

   interface FastEthernet0/24
    switchport trunk encapsulation dot1q
    switchport mode trunk

This is the trunked port.  A typical VLAN port looks like this:

   interface FastEthernet0/1
    switchport access vlan 3
   !

If you have:

   interface FastEthernet0/2
    switchport access vlan 3
   !

then traffic across FastEthernet0/1 will be duplicated across 
FastEthernet0/2 to make the VLAN, but the 'leaking' you describe 
shouldn't happen, unless it's a trunked port.

Specifically, if you have:

   interface FastEthernet0/3
    switchport access vlan 4
   !

Then FastEthernet0/3 should never see traffic for vlan 3 unless it's 
broadcast traffic and client machines are on the same subnet.

As Kevin mentioned, ports not assigned a VLAN id are on the default 
VLAN.  type:

   vlan database
   show

and you'll see something like:

   VLAN ISL Id: 1
     Name: default
     Media Type: Ethernet
     VLAN 802.10 Id: 100001
     State: Operational
     MTU: 1500
     Translational Bridged VLAN: 1002
     Translational Bridged VLAN: 1003

plus whatever other VLAN's are defined.

-Bill
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