• The cost of a spanning tree bundle port is always 10000. It is not affected by any of the following:
• Number or speed of the bundle members
• Logical or administrative operational status of the bundle member ports
• Addition or deletion of bundle members
• Receiving BPDU on an interface configured with the BPDU Guard error-disables the physical interface
as well as any layer-2 or layer-3 sub-interfaces configured on the physical interface.
• Only Ethernet Flow-points (EFPs) that are untagged or have a single VLAN tag can be protected by
PVRST.
• If any one EFP in a bridge-domain is protected by PVRST, then all EFPs in that bridge domain must
belong to the same VLAN.
• If any one EFP on a port is protected by PVRST, then all EFPs on that port must be protected by PVRST.
• PVRST supports up to 8000 Port Tree Instances (PTIs) per line card and 16000 PTIs per system. PTI
refers to the product of the number of ports and VLANs. PVRST supports 1000 VLANs.
Multiple VLAN Registration Protocol
The Multiple VLAN Registration Protocol is defined in IEEE 802.1ak and is used in MSTP based networks
to optimize the propagation of multicast and broadcast frames.
By default, multicast and broadcast frames are propagated to every point in the network, according to the
spanning tree, and hence to every edge (host) device that is attached to the network. However, for a given
VLAN, it may be the case that only certain hosts are interested in receiving the traffic for that VLAN.
Furthermore, it may be the case that a given network device, or even an entire segment of the network, has
no attached hosts that are interested in receiving traffic for that VLAN. In this case, an optimization is possible
by avoiding propagating traffic for that VLAN to those devices that have no stake in it. MVRP provides the
necessary protocol signaling that allows each host and device to indicate to its attached peers which VLANs
it is interested in.
MVRP-enabled devices can operate in two modes:
• Static mode—In this mode, the device initiates MVRP messages declaring interest in a statically configured
set of VLANs. Note that the protocol is still dynamic with respect to the MSTP topology; it is the set of
VLANs that is static.
• Dynamic mode—In this mode, the device processes MVRP messages received on different ports, and
aggregates them dynamically to determine the set of VLANs it is interested in. It sends MVRP messages
declaring interest in this set. In dynamic mode, the device also uses the received MVRP messages to
prune the traffic sent out of each port so that traffic is only sent for the VLANs that the attached device
has indicated it is interested in.
Cisco ASR 9000 Series Routers support operating in static mode. This is known as MVRP-lite.
How to Implement Multiple Spanning Tree Protocol
This section contains these procedures:
L2VPN and Ethernet Services Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x
425
Implementing Multiple Spanning Tree Protocol
Multiple VLAN Registration Protocol
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