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Features in JUNOS Software for EX-series Switches, Release 9.1

Date: 28 October 2008

This page describes the features in Release 9.1 of JUNOS software for EX-series switches.

Bridging, VLANs, and Spanning Trees

  • BPDU protection—A loop-free network in a spanning-tree topology is supported through the exchange of a special type of frame called bridge protocol data unit (BPDU). Receipt of BPDUs on certain interfaces in an STP, RSTP, or MSTP topology, however, can lead to network outages. Enable BPDU protection on those interfaces to prevent these outages.

    Enable BPDU protection on STP interfaces and non-STP interfaces to prevent spoofed BPDU packets from entering a domain. When a BPDU-protected interface receives BPDUs, it transitions to a BPDU inconsistent state, disabling an interface and preventing it from forwarding traffic. The interface can be returned to service again automatically by configuring a timer or manually using the operational mode command clear ethernet-switching bpdu-error. For more information, see Understanding BPDU Protection for STP, RSTP, and MSTP on EX-series Switches.

  • Root protection—Root protection lets network administrators manually enforce the root bridge placement in the network. Enable root protection on interfaces that should not receive superior BPDUs from the root bridge and should not be elected as the root port. If the bridge receives superior STP BPDUs on an interface that has root protection enabled, that interface transitions to a root-prevented STP state (inconsistency state) and the interface is blocked. This blocking prevents a bridge that should not be the root bridge from being elected the root bridge.

    After the bridge stops receiving superior STP BPDUs on the interface with root protection, it automatically transitions back to a forwarding state.

    When root protection is enabled on an interface, it is enabled for all the STP instances on that interface. The interface is blocked only for instances for which it receives superior BPDUs. Otherwise, it participates in the spanning-tree topology.

    An interface can be configured for either root protection or loop protection, but not for both. For more information, see Understanding Root Protection for STP, RSTP, and MSTP on EX-series Switches.

  • Loop protection—STP loop protection provides additional protection against Layer 2 forwarding loops in STP domains. When loop protection is enabled, the spanning-tree topology detects root ports and blocked ports and makes sure both keep receiving BPDUs. If a loop-protection-enabled interface stops receiving BPDUs from its designated port, it reacts as it would react to a problem with the physical connection on this interface. It does not transition the interface to a forwarding state, but instead transitions it to a loop-inconsistent state. The interface recovers and then it transitions back to the spanning-tree blocking state as soon as it receives a BPDU. An interface can be configured for either root protection or loop protection, but not for both. For more information, see Understanding Loop Protection for STP, RSTP, and MSTP on EX-series Switches.
  • Storm control—Storm control prevents a rogue switch from generating traffic storms that might bring down a LAN. Enable storm control to permit the switch to monitor traffic levels and drop packets when a specified traffic level is exceeded, thus preventing packets from proliferating and degrading the LAN. For more information, see Understanding Storm Control on EX-series Switches.

Layer 3 Protocols

  • IGMP snooping—Internet Group Management Protocol (IGMP) snooping regulates multicast traffic in a switched network. With IGMP snooping enabled, a LAN switch monitors the IGMP transmissions between a host and multicast router, keeping track of the multicast groups and associated member ports. The switch uses that information to make intelligent multicast-forwarding decisions and forward traffic to the intended destination interfaces. EX-series switches support IGMP versions 1 and 2. Note that EX-series switches do not support IGMPv3. For more information, see IGMP Snooping on EX-series Switches Overview.

Management and RMON