From: Victor Cappuccio (vcappuccio@ccbootcamp.com)
Date: Wed Jul 25 2007 - 14:58:11 ART
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
This archive was generated by hypermail 2.1.4 : Sat Aug 18 2007 - 08:17:42 ART