From: Kirit Bhamre (kirit4144@gmail.com)
Date: Wed Jul 25 2007 - 15:49:02 ART
I think it is done using VTP messages...
Check this link...
http://www.cisco.com/en/US/docs/switches/lan/catalyst4000/7.1/configuration/guide/vtp.html#wp1019843
On 7/25/07, Mounir Mohamed <mounir.mohamed@gmail.com> wrote:
>
> Does anyboy know which method used by the switches to advertise thier
> active
> VLANs and re-advertise for delete or added VLANs!!!
> (CDP frames or VTP messages or !!!
>
>
> On 7/25/07, Victor Cappuccio <vcappuccio@ccbootcamp.com> wrote:
> >
> > Hi Ajay,
> >
> > http://en.wikipedia.org/wiki/VTP#VLAN_Pruning
> >
> > VTP can prune unneeded VLANs from trunk links. VTP maintains a map of
> > VLANs
> > and switches, enabling traffic to be directed only to those switches
> known
> > to
> > have ports on the intended VLAN. This enables more efficient use of
> trunk
> > bandwidth.
> >
> > Each switch will advertise which VLAN's it has active to neighboring
> > switches.
> > The neighboring switches will then "prune" VLAN's that are not active
> > across
> > that trunk, thus saving bandwidth. If a VLAN is then added to one of the
> > switches, the switch will then re-advertise it's active VLAN's so that
> > pruning
> > can be updated by its neighbors. For this to work, VLAN pruning must be
> > enabled on both ends of the trunk. It is easiest to enable VLAN pruning
> > for an
> > entire VTP management domain by simply enabling it on one of the VTP
> > servers
> > for that domain. To enable VLAN pruning for a VTP domain, enter the
> > following
> > command on a VTP server for that domain...
> >
> > VTP_Server_Sw1(config)# vtp pruning
> >
> > This will then propagate to all switches in the vtp domain.
> >
> >
> > Couple of good links:
> >
> > http://www.cisco.com/warp/public/473/21.html <-- far way good peace of
> > document (with swf included :D)
> >
> >
> www.cisco.com/univercd/cc/td/doc/product/lan/cat5000/rel_4_2/config/vlans.htm
> > www.ciscopress.com/articles/article.asp?p=29803&seqNum=4
> >
> > Having this topology
> >
> > sw1 Sw2
> > | |
> > Sw3 - Sw4
> >
> > Sw3#conf ter
> > Enter configuration commands, one per line. End with CNTL/Z.
> > Sw3(config)#vtp pruning
> > Cannot modify pruning unless in VTP server mode
> > Sw3(config)#do show vtp Mode
> > Sw3(config)#do show vtp status | in Mode
> > VTP Operating Mode : Client
> > VTP Pruning Mode : Disabled
> > VTP V2 Mode : Disabled
> > Sw3(config)#
> >
> > The configuration of trunk links (using protocols like ISL or .1q )
> allows
> > traffic from multiple VLANs to travel across this links, this is not
> > always
> > optimal
> >
> > Sw3(config)#do show int trunk
> >
> > Port Mode Encapsulation Status Native vlan
> > Fa0/19 on 802.1q trunking 1
> > Fa0/20 on 802.1q trunking 1
> > Fa0/21 on 802.1q trunking 1
> > Fa0/22 on 802.1q trunking 1
> >
> > Port Vlans allowed on trunk
> > Fa0/19 1-4094
> > Fa0/20 1-4094
> > Fa0/21 1-4094
> > Fa0/22 1-4094
> >
> > Port Vlans allowed and active in management domain
> > Fa0/19 1,12,100,104,106,149,156,237,735
> > Fa0/20 1,12,100,104,106,149,156,237,735
> > Fa0/21 1,12,100,104,106,149,156,237,735
> > Fa0/22 1,12,100,104,106,149,156,237,735
> > ---------------------------------------------------> All Traffic for the
> > different vlans pass over the trunk by default
> > Port Vlans in spanning tree forwarding state and not pruned
> > Fa0/19 1,12,100,104,106,149,156,237,735
> > Fa0/20 1,12,100,104,106,149,156,237,735
> > Fa0/21 1,12,100,104,106,149,156,237,735
> >
> > Port Vlans in spanning tree forwarding state and not pruned
> > Fa0/22 none
> >
> >
> >
> > Sw3(config)#do show vlan
> >
> > VLAN Name Status Ports
> > ---- -------------------------------- ---------
> > -------------------------------
> > 1 default active Fa0/1, Fa0/2, Fa0/3,
> Fa0/4
> > Fa0/5, Fa0/6, Fa0/7,
> Fa0/8
> > Fa0/9, Fa0/10, Fa0/11,
> > Fa0/12
> > Fa0/13, Fa0/14, Fa0/15,
> > Fa0/16
> > Fa0/17, Fa0/18, Fa0/23,
> > Fa0/24
> > Gi0/1, Gi0/2
> > 12 VLAN0012 active
> > 100 VLAN0100 active
> > 104 VLAN0104 active
> > 106 VLAN0106 active
> > 149 VLAN0149 active
> > 156 VLAN0156 active
> > 237 VLAN0237 active
> > 735 VLAN0735 active
> > 1002 fddi-default act/unsup
> > 1003 token-ring-default act/unsup
> > 1004 fddinet-default act/unsup
> > 1005 trnet-default act/unsup
> >
> > VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Trans1
> > Trans2
> > ---- ----- ---------- ----- ------ ------ -------- ---- -------- ------
> > ------
> > 1 enet 100001
> 1500 - - - - - 0 0
> > 12 enet 100012
> 1500 - - - - - 0 0
> > 100 enet 100100
> 1500 - - - - - 0 0
> > 104 enet 100104
> 1500 - - - - - 0 0
> > 106 enet 100106
> 1500 - - - - - 0 0
> > 149 enet 100149
> 1500 - - - - - 0 0
> > 156 enet 100156
> 1500 - - - - - 0 0
> > 237 enet 100237
> 1500 - - - - - 0 0
> > 735 enet 100735
> 1500 - - - - - 0 0
> > 1002 fddi 101002
> 1500 - - - - - 0 0
> > 1003 tr 101003
> 1500 - - - - srb 0 0
> > 1004 fdnet 101004 1500 - - - ieee
> - 0 0
> > 1005 trnet 101005
> 1500 - - - ibm - 0 0
> >
> > Remote SPAN VLANs
> >
> >
> -----------------------------------------------------------------------------
> > -
> >
> >
> > Primary Secondary Type Ports
> > ------- --------- -----------------
> > ------------------------------------------
> >
> > Sw3(config)#
> >
> >
> > if we enable prunning in our network
> >
> > Sw1(config)#vtp prun
> > Pruning switched on
> >
> > then we have a different result
> > Sw3(config)#do show int trunk
> >
> > Port Mode Encapsulation Status Native vlan
> > Fa0/19 on 802.1q trunking 1
> > Fa0/20 on 802.1q trunking 1
> > Fa0/21 on 802.1q trunking 1
> > Fa0/22 on 802.1q trunking 1
> >
> > Port Vlans allowed on trunk
> > Fa0/19 1-4094
> > Fa0/20 1-4094
> > Fa0/21 1-4094
> > Fa0/22 1-4094
> >
> > Port Vlans allowed and active in management domain
> > Fa0/19 1,12,100,104,106,149,156,237,735
> > Fa0/20 1,12,100,104,106,149,156,237,735
> > Fa0/21 1,12,100,104,106,149,156,237,735
> > Fa0/22 1,12,100,104,106,149,156,237,735
> > -------------------------------------------------------------------->
> now
> > the
> > traffic get allocated in the best path to send the Unknown traffic /
> > Multicast-Broadcast
> > Port Vlans in spanning tree forwarding state and not pruned
> > Fa0/19 1,104,237
> > Fa0/20 1
> > Fa0/21 1,12,100,104,149,156,237,735
> >
> > Port Vlans in spanning tree forwarding state and not pruned
> > Fa0/22 none
> > Sw3(config)#
> >
> > now lets create a new vlan in Sw1 (VTP Server of this domain) and lets
> > assign
> > that to a port in Sw3
> >
> > Sw1(config)#vlan 13
> > Sw1(config-vlan)#exit
> > Sw1(config)#do show int trunk
> >
> > Port Mode Encapsulation Status Native vlan
> > Fa0/19 on 802.1q trunking 1
> > Fa0/20 on 802.1q trunking 1
> > Fa0/21 on 802.1q trunking 1
> > Fa0/22 on 802.1q trunking 1
> >
> > Port Vlans allowed on trunk
> > Fa0/19 1-4094
> > Fa0/20 1-4094
> > Fa0/21 1-4094
> > Fa0/22 1-4094
> >
> > Port Vlans allowed and active in management domain
> > Fa0/19 1,12-13,100,104,106,149,156,237,735 -------------------->
> > Vlan
> > 13 here
> > Fa0/20 1,12-13,100,104,106,149,156,237,735
> > Fa0/21 1,12-13,100,104,106,149,156,237,735
> > Fa0/22 1,12-13,100,104,106,149,156,237,735
> >
> > ---------------------------------------------------------------------->
> > but
> > V13 is not down here.
> > Port Vlans in spanning tree forwarding state and not pruned
> > Fa0/19 1,12,104,149,156,237,735
> > Fa0/20 1
> > Fa0/21 1,104,149,237
> >
> > Port Vlans in spanning tree forwarding state and not pruned
> > Fa0/22 1
> > Sw1(config)#
> >
> > Now lets assign that Vlan to a couple of ports int sw1 -to- sw4
> >
> > Sw1(config-if)#int f0/5
> > Sw1(config-if)#sw a vlan 13
> > Sw1(config-if)#exit
> > Sw1(config)#do show int trunk
> >
> > Port Mode Encapsulation Status Native vlan
> > Fa0/19 on 802.1q trunking 1
> > Fa0/20 on 802.1q trunking 1
> > Fa0/21 on 802.1q trunking 1
> > Fa0/22 on 802.1q trunking 1
> >
> > Port Vlans allowed on trunk
> > Fa0/19 1-4094
> > Fa0/20 1-4094
> > Fa0/21 1-4094
> > Fa0/22 1-4094
> >
> > Port Vlans allowed and active in management domain
> > Fa0/19 1,12-13,100,104,106,149,156,237,735
> > Fa0/20 1,12-13,100,104,106,149,156,237,735
> > Fa0/21 1,12-13,100,104,106,149,156,237,735
> > Fa0/22 1,12-13,100,104,106,149,156,237,735
> >
> > Port Vlans in spanning tree forwarding state and not pruned
> > Fa0/19 1,12,104,149,156,237,735
> > Fa0/20 1
> > Fa0/21 1,104,149,237
> >
> > Port Vlans in spanning tree forwarding state and not pruned
> > Fa0/22 1
> >
> >
> > Sw3(config)#int f0/7
> > Sw3(config-if)#sw host
> > switchport mode will be set to access
> > spanning-tree portfast will be enabled
> > channel group will be disabled
> >
> > Sw3(config-if)#sw a vlan 13
> > Sw3(config-if)#no sh
> > Sw3(config-if)#do show vlan id 13
> >
> > VLAN Name Status Ports
> > ---- -------------------------------- ---------
> > -------------------------------
> > 13 VLAN0013 active Fa0/7, Fa0/19, Fa0/20,
> > Fa0/21
> > Fa0/22
> >
> > VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Trans1
> > Trans2
> > ---- ----- ---------- ----- ------ ------ -------- ---- -------- ------
> > ------
> > 13 enet 100013
> 1500 - - - - - 0 0
> >
> > Remote SPAN VLAN
> > ----------------
> > Disabled
> >
> > Primary Secondary Type Ports
> > ------- --------- -----------------
> > ------------------------------------------
> > Sw3(config-if)#do show int trunk
> >
> > Port Mode Encapsulation Status Native vlan
> > Fa0/19 on 802.1q trunking 1
> > Fa0/20 on 802.1q trunking 1
> > Fa0/21 on 802.1q trunking 1
> > Fa0/22 on 802.1q trunking 1
> >
> > Port Vlans allowed on trunk
> > Fa0/19 1-4094
> > Fa0/20 1-4094
> > Fa0/21 1-4094
> > Fa0/22 1-4094
> >
> > Port Vlans allowed and active in management domain
> > Fa0/19 1,12-13,100,104,106,149,156,237,735
> > Fa0/20 1,12-13,100,104,106,149,156,237,735
> > Fa0/21 1,12-13,100,104,106,149,156,237,735
> > Fa0/22 1,12-13,100,104,106,149,156,237,735
> >
> > -------------------------------------------------------------------> now
> > vlan
> > 13 traffic is send out port f0/21 for unknown/multicast traffic
> >
> > Port Vlans in spanning tree forwarding state and not pruned
> > Fa0/19 1,104,237
> > Fa0/20 1
> > Fa0/21 1,12-13,100,104,149,156,237,735
> >
> > Port Vlans in spanning tree forwarding state and not pruned
> > Fa0/22 none
> > Sw3(config-if)#
> >
> > When VTP Pruning is implemented in a VTP management domain, traffic for
> a
> > given VLAN is only passed to a switch across a trunk link if necessary
> >
> > HTH
> >
> > thanks,
> > Victor Cappuccio.-
> > - CCSI# 31452
> >
> > Network Learning Inc - A Cisco Sponsored Organization (SO) YES! We take
> > Cisco Learning credits!
> > vcappuccio@ccbootcamp.com
> > http://www.ccbootcamp.com (Cisco Training and Rental Racks)
> > Voice: 702-968-5100
> > FAX: 702-446-8012
> >
> >
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com on behalf of Ajay Prakash
> > Sent: Wed 25-Jul-07 2:13 AM
> > To: Cisco certification
> > Cc: Ajay Prakash
> > Subject: VTP Pruning
> >
> > Hello,
> >
> > I have a query regarding VTP pruning.
> >
> > ____________________________ SW2
> > |
> > |
> > SW1--------------------------------------------- SW3
> > |
> > |____________________________ SW4
> >
> >
> > SW1 has trunk links to SW2, SW3 and SW4. We want the switches to prune
> > vlans
> > for which they do not have any ports assigned and the requirement tells
> us
> > to
> > do it in minimum number of commands (IE lab 2)
> >
> > I had enabled VTP pruning on all 4 switches but when I checked the
> > solution
> > in
> > the workbook, they have enabled pruning just on SW1. My understanding
> was
> > that
> > if a switch does not use a vlan, it sends the prune message and hence it
> > should be configured on all 4 switched.
> >
> > Any inputs regarding this would be greatly appreciated.
> >
> > Regards,
> > Ajay Prakash
> >
> > _______________________________________________________________________
> > Subscription information may be found at:
> > http://www.groupstudy.com/list/CCIELab.html
> >
> > _______________________________________________________________________
> > Subscription information may be found at:
> > http://www.groupstudy.com/list/CCIELab.html
> >
>
>
>
> --
> Best Reagrds,
> Mounir Mohamed
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
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