Cisco Catalyst 2960 Series, Configuration Manual

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Related Topics
Enabling the VTP Version , on page 2097
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.
VTP pruning blocks unneeded flooded traffic to VLANs on trunk ports that are included in the pruning-eligible
list. Only VLANs included in the pruning-eligible list can be pruned. By default, VLANs 2 through 1001 are
pruning eligible switch trunk ports. If the VLANs are configured as pruning-ineligible, the flooding continues.
VTP pruning is supported in all VTP versions.
With VTP versions 1 and 2, when you enable pruning on the VTP server, it is enabled for the entire VTP
domain. In VTP version 3, you must manually enable pruning on each switch in the domain. Making VLANs
pruning-eligible or pruning-ineligible affects pruning eligibility for those VLANs on that trunk only (not on
all switches in the VTP domain).
VTP pruning takes effect several seconds after you enable it. VTP pruning does not prune traffic from VLANs
that are pruning-ineligible. VLAN 1 and VLANs 1002 to 1005 are always pruning-ineligible; traffic from
these VLANs cannot be pruned. Extended-range VLANs (VLAN IDs higher than 1005) are also
pruning-ineligible.
Related Topics
Enabling VTP Pruning , on page 2099
VTP and Switch Stacks
The switch supports homogeneous stacking and mixed stacking. Mixed stacking is supported only with
the Catalyst 2960-S switches. A homogenous stack can have up to eight stack members, while a mixed
stack can have up to four stack members. All switches in a switch stack must be running the LAN Base
image.
Note
VTP configuration is the same in all members of a switch stack. When the switch stack is in VTP server or
client mode, all switches in the stack carry the same VTP configuration. When VTP mode is transparent, the
stack is not taking part in VTP.
• When a switch joins the stack, it inherits the VTP and VLAN properties of the active switch.
• All VTP updates are carried across the stack.
• When VTP mode is changed in a switch in the stack, the other switches in the stack also change VTP
mode, and the switch VLAN database remains consistent.
VTP version 3 functions the same on a standalone switch or a stack except when the switch stack is the primary
server for the VTP database. In this case, the MAC address of the active switch is used as the primary server
ID. If the active switch reloads or is powered off, a new active switch is elected.
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
2089
Information About VTP