CCIE Routing & Switching v5 Workbook -
CCIE R&S v5 Advanced Technology Labs -
LAN Switching
VTP Pruning
A Note On Section Initial Configuration Files: You must load the
initial configuration files for the section, named LAN Switching Initial
VTP, which can be found in
. Reference the Virtual Routers & Physical Switches
Diagram to complete this task.
Task
All switches are pre-configure in VTP domain CCIE.
Ensure that SW1 is in VTP client mode.
Enable VTP pruning in the Layer 2 network so that inter-switch broadcast replication
is minimized.
Verify that this configuration is functional through the
show interface trunk
output.
Configuration
SW1:
vtp mode client
SW2:
vtp pruning
Verification
VTP pruning eliminates the need to statically remove VLANs from the allowed
trunking list of a port by having the switches automatically communicate to each
other which VLANs they have locally assigned or are in the transit path for.
The
show interface pruning
command indicates what traffic the local switch told its
neighbor that it needs, via the VLAN traffic requested of neighbor field. These
VLANs are either locally assigned to certain ports, or those for which the local
switch is in the Layer 2 transit path and traffic was requested by neighbor switches.
The Vlans pruned for lack of request by neighbor field indicates the VLANs that
the upstream neighbor did not request. VTP pruning can be enabled only on the
device running in server mode, and the settings will be inherited by all devices in the
same VTP domain.
In the below output, this means that SW1 is not forwarding VLAN 7 to SW3,
because SW3 did not request it. This output can be confusing because what SW1
sees as pruned for lack of request is the opposite of what SW3 sees as requested.
SW1#show interface fastethernet0/19 pruning
PortVlans pruned for lack of request by neighborFa0/195,7-10,22,43,58,67,79,123,146
PortVlan traffic requested of neighborFa0/191,5,7-10,22,43,58,67,79,123,146
!
!SW3#show interface fastethernet0/19 pruning
PortVlans pruned for lack of request by neighborFa0/19none
PortVlan traffic requested of neighborFa0/19none
If the network is converged, all devices in the VTP domain should agree that pruning
is enabled, as shown in the below
show vtp status
output. Note that transparent
switches cannot participate in pruning because they do not read the payload of the
VTP updates they are receiving from their adjacent neighbors, they just relay it.
SW1#show vtp status
VTP Version capable
: 1 to 3
VTP version running
: 1
VTP Domain Name
: CCIEVTP Pruning Mode: Enabled
VTP Traps Generation
: Disabled
Device ID
: 000a.b832.3580
Configuration last modified by 0.0.0.0 at 3-1-93 05:42:56
Feature VLAN:
--------------
VTP Operating Mode
: Client
Maximum VLANs supported locally
: 1005
Number of existing VLANs
: 17
Configuration Revision
: 3
MD5 digest
: 0xC0 0x28 0xD7 0xD0 0x3D 0xA3 0x1D 0xB7
0x13 0xC9 0xD1 0xE6 0x57 0xD0 0x09 0x58
!
!SW2#show vtp status
VTP Version capable
: 1 to 3
VTP version running
: 1
VTP Domain Name
: CCIEVTP Pruning Mode: Enabled
VTP Traps Generation
: Disabled
Device ID
: 001c.576d.4a00
Configuration last modified by 0.0.0.0 at 3-1-93 05:42:56
Local updater ID is 0.0.0.0 (no valid interface found)
Feature VLAN:
--------------
VTP Operating Mode
: Server
Maximum VLANs supported locally
: 1005
Number of existing VLANs
: 17
Configuration Revision
: 3
MD5 digest
: 0xC0 0x28 0xD7 0xD0 0x3D 0xA3 0x1D 0xB7
0x13 0xC9 0xD1 0xE6 0x57 0xD0 0x09 0x58
!
!SW3#show vtp status
VTP Version capable
: 1 to 3
VTP version running
: 1
VTP Domain Name
: CCIEVTP Pruning Mode: Enabled
VTP Traps Generation
: Disabled
Device ID
: 001d.45cc.0580
Configuration last modified by 0.0.0.0 at 3-1-93 05:42:56
Feature VLAN:
--------------
VTP Operating Mode
: Client
Maximum VLANs supported locally
: 1005
Number of existing VLANs
: 17
Configuration Revision
: 3
MD5 digest
: 0xC0 0x28 0xD7 0xD0 0x3D 0xA3 0x1D 0xB7
0x13 0xC9 0xD1 0xE6 0x57 0xD0 0x09 0x58
!
!SW4#show vtp status
VTP Version capable
: 1 to 3
VTP version running
: 1
VTP Domain Name
: CCIEVTP Pruning Mode: Enabled
VTP Traps Generation
: Disabled
Device ID
: 001c.576d.3d00
Configuration last modified by 0.0.0.0 at 3-1-93 05:42:56
Feature VLAN:
--------------
VTP Operating Mode
: Client
Maximum VLANs supported locally
: 1005
Number of existing VLANs
: 17
Configuration Revision
: 3
MD5 digest
: 0xC0 0x28 0xD7 0xD0 0x3D 0xA3 0x1D 0xB7
0x13 0xC9 0xD1 0xE6 0x57 0xD0 0x09 0x58
To quickly view the traffic that is not being pruned, and therefore actually forwarded,
issue the
show interface trunk
command. The final field of Vlans in spanning tree
forwarding state and not pruned means that the VLAN is created, is allowed on
the link, is running STP, and is not pruned.
SW1#show interface trunk | begin pruned
PortVlans in spanning tree forwarding state and not pruned
Fa0/191
Fa0/201
Fa0/211
Fa0/221Fa0/231,5,7-10,22,43,58,67,79,123,146
Fa0/241,5,7-10,22,43,58,67,79,123,146
!
!SW2#show interface trunk | begin pruned
PortVlans in spanning tree forwarding state and not pruned
Fa0/231,5,7-10,22,43,58,67,79,123,146
Fa0/24none
!
!SW3#show interface trunk | begin pruned
PortVlans in spanning tree forwarding state and not pruned
Fa0/191,5,7-10,22,43,58,67,79,123,146
Fa0/20none
!
!SW4#show interface trunk | begin pruned
PortVlans in spanning tree forwarding state and not pruned
Fa0/211,5,7-10,22,43,58,67,79,123,146
Fa0/22none