From: Mohammad Saeed (mzsaeed@gmail.com)
Date: Thu May 24 2007 - 14:15:56 ART
In my opinion, as no Pruning is in place, all VLANS will be allowed on
trunk link and flooded traffic from all VLANS will pass through the
trunk even if the respective VLAN does not exist on the other switch.
So, if that VLAN does not exist on the other switch traffic will
dropped. This is where Pruning comes, if you want to let the traffic
pass on the trunk only for the VLANS that exist on the other end,
enable VTP pruning on both switches.
By default 802.1Q trunk tag all VLANS traffic except the Native VLAN,
so as per this rule, if traffic is flooded in VLAN 10, suppose, when
it will cross the Dot1Q trunk it shall be tagged with the respective
VLAN ID, VLAN 10, so that receiving switch shall be able to contain
the traffic in the VLAN 10.
Hope this helps.
Regards,
Mohammad Zahed Saeed
On 5/24/07, Gustavo Novais <gustavo.novais@novabase.pt> wrote:
> Hello,
>
>
>
> Lately I faced a doubt while on a customer audit, that although does not
> affect performance, has left me thinking...
>
>
>
> You have two switches (lets say 3550 and 2950) in VTP mode transparent,
> interconnected through a dot1q trunk, without any vlan filtering on the
> trunk ports, but both switches have different vlan databases. Some vlans
> in common, some not.
>
>
>
> What will happen to the flooded traffic on those trunk ports on the
> not-in-common (nic) vlans?
>
>
>
> Sh interface trunk tells me that not-in-common vlans are STP forwarding
> and are obviously allowed on the trunk.
>
>
>
> Will the flooded traffic for one of those vlans cross the patch cable
> (tagged), and be dropped by the other switch, who doesn't know that vlan
> ID?
>
> Or will it simply not be forwarded over that particular link?
>
> Or will it be flooded through the trunks native vlan (on the receiving
> switch)?
>
>
>
> Any ideas/comments/links pointing to info are helpful.
>
>
>
> Thanks
>
>
>
> Gustavo Novais
>
> #15622
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
This archive was generated by hypermail 2.1.4 : Fri Jun 01 2007 - 06:55:22 ART