06-08-2006 02:22 AM - edited 03-03-2019 03:33 AM
Hi
If I have switch (switch 3) in a network which only has vlan 2 and 3 listed in its vlan database. If I have atrunk link to other switches that have other vlans listed in their respective vlan databasese, would switch 3 forward those other vlans via its trunk link, even though the vlan's aren't listed in its database?
Thanks for any help.
Dan
Solved! Go to Solution.
06-08-2006 02:38 AM
yes dan,
your VLAN information will travel through the trunk to the other switch even there is no same vlan on other switch...if you want to prevent that unnessesary information of VLAN travel through the switch then you have to configure the VLAN PRUNING...
you will get more idea about it from following link
this link will give you idea
http://www.cisco.com/warp/public/473/11.html
and this will usefull for configuration
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat5000/rel_4_2/config/vlans.htm#xtocid798016
remember to rate this post if it helps
regards
Devang
06-08-2006 02:38 AM
yes dan,
your VLAN information will travel through the trunk to the other switch even there is no same vlan on other switch...if you want to prevent that unnessesary information of VLAN travel through the switch then you have to configure the VLAN PRUNING...
you will get more idea about it from following link
this link will give you idea
http://www.cisco.com/warp/public/473/11.html
and this will usefull for configuration
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat5000/rel_4_2/config/vlans.htm#xtocid798016
remember to rate this post if it helps
regards
Devang
06-08-2006 02:45 AM
dan its word VTP pruning
this is also good one
http://www.networknewz.com/2004/0317.html
rate the post if it helps
regards
Devang
06-08-2006 03:30 AM
Just to add that only broadcast , unknown unicast and multicast will travel to the other switch.
Vlad
06-08-2006 03:28 AM
Hello Dan,
I traffic for other vlans will travel to the other switch if the vlan is a native vlan (when using dot1q) or when its a broadcast.
Not all traffic will travel to the other switch.
Anyway, if you need to restric traffic there're 2 options:
switchport trunk allowed vlan {add | all | except | remove} vlan-list
or vtp pruning.
"VTP pruning increases network available bandwidth by restricting flooded traffic to those trunk links that the traffic must use to reach the destination devices. Without VTP pruning, a switch floods broadcast, multicast, and unknown unicast traffic across all trunk links within a VTP domain even though receiving switches might discard them. VTP pruning is disabled by default."
Its always a good practice to only let the needed vlan to cross the trunk links.
HTH,
if it does, please rate this post.
Vlad
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