Supported Platforms
Understanding Multiple VLAN Registration Protocol (MVRP) on EX Series Switches
Multiple VLAN Registration Protocol (MVRP) is a Layer 2 messaging protocol that manages the addition, deletion, and renaming of active virtual LANs, thereby reducing network administrators’ time spent on these tasks. Use MVRP on Juniper Networks EX Series Ethernet Switches to dynamically register and unregister active VLANs on trunk interfaces. Using MVRP means that you do not have to manually register VLANs on all connections—that is, you do not need to explicitly bind a VLAN to each trunk interface. With MVRP, you configure a VLAN on one switch interface and the VLAN configuration is distributed through all active switches in the domain.
MVRP is an application protocol of the Multiple Registration Protocol (MRP) and is defined in the IEEE 802.1ak standard. MRP and MVRP replace Generic Attribute Registration Protocol (GARP) and GARP VLAN Registration Protocol (GVRP) and overcome GARP and GVRP limitations.
This topic describes:
How MVRP Updates, Creates, and Deletes VLANs on the Switches
When any MVRP-member VLAN is changed, that VLAN sends a protocol data unit (PDU) to all other MVRP-member active VLANs. The PDU informs the other VLANs which switches and interfaces currently belong to the sending VLAN. This way, all MVRP-member VLANs are always updated with the current VLAN state of all other MVRP-member VLANs. Timers dictate when PDUs can be sent and when switches receiving MVRP PDUs can update their MVRP VLAN information.
In addition to sending PDU updates, MVRP dynamically creates VLANs on member interfaces when a new VLAN is added to any one interface. This way, VLANs created on one member switch are propagated to other member switches as part of the MVRP message exchange process.
To keep VLAN membership information current, MVRP removes switches and interfaces when they become unavailable. Pruning VLAN information has these benefits:
- Limits the network VLAN configuration to active participants, thereby reducing network overhead.
- Limits broadcast, unknown unicast, and multicast (BUM) traffic to interested devices.
MVRP Is Disabled by Default on the Switches
MVRP is disabled by default on the switches and, when enabled, affects only trunk interfaces. Once you enable MVRP, all VLAN interfaces on the switch belong to MVRP (the default normal mode) and those interfaces accept PDU messages and send their own PDU messages. To prevent one or more interfaces from participating in MVRP, you can specifically configure an interface to forbidden mode instead of the default normal mode.
VLAN updating, dynamic VLAN configuration through MVRP, and VLAN pruning are all active on trunk interfaces when MVRP is enabled.
MRP Timers Control MVRP Updates
MVRP registration and updates are controlled by timers that are part of the MRP. These timers are set on a per-interface basis and define when MVRP PDUs can be sent and when MVRP information can be updated on a switch.
The following MRP timers are used to control the operation of MVRP:
- Join timer—Controls the interval for the next MVRP PDU transmit opportunity.
- Leave timer—Controls the period of time that an interface on the switch waits in the leave state before changing to the unregistered state.
- LeaveAll timer—Controls the frequency with which the interface generates LeaveAll messages.
 | Best Practice: Unless there is a compelling reason to change the timer settings, leave the default settings in place. Modifying timers to inappropriate values can cause an imbalance in the operation of MVRP. |
MVRP Uses MRP Messages to Transmit Switch and VLAN States
MVRP uses MRP messages to register and declare MVRP states for a switch or VLAN and to inform the switching network that a switch or VLAN is leaving MVRP. These messages are communicated as part of the PDU sent by any switch interface to the other switches in the network.
The following MRP messages are communicated for MVRP:
- Empty—MVRP information is not declared and no VLAN is registered.
- In—MVRP information is not declared but a VLAN is registered.
- JoinEmpty—MVRP information is declared but no VLAN is registered.
- JoinIn—MVRP information is declared and a VLAN is registered.
- Leave—MVRP information that was previously declared is withdrawn.
- LeaveAll—Unregister all VLANs on the switch. VLANs must re-register to participate in MVRP.
- New—The MVRP information is new and a VLAN might not be registered yet.
Compatibility Issues With Junos OS Release 11.3 and Later
Prior to Junos OS Release 11.3, the protocol data units (PDUs) sent and received by MVRP contained an extra byte. This extra byte in the PDUs prevented MVRP from conforming to the IEEE standard 802.1ak and was removed in Release 11.3 to make MVRP running on Junos OS compatible with the standard. If all switches in your network are running Release 11.3, you will see no change in MVRP operation and there are no steps you need to take to continue using MVRP. If your network is running only Release 11.2 or earlier, you also do not need to do anything to continue using MVRP.
If your network is running a mix of Release 11.3 and earlier releases, you need to take steps to make your switches compatible when using MVRP. Switches running a version of Junos OS earlier than Release 11.3 require the extra MVRP byte to be part of each PDU they receive—they will not recognize a PDU with this byte missing. You can determine whether the switches in your network are running incompatible versions of MVRP by issuing the show mvrp statistics command. For more information on diagnosing and correcting this MVRP compatibility situation, see Configuring Multiple VLAN Registration Protocol (MVRP) (CLI Procedure).
