Specifications

Alcatel-Lucent Page 18
OmniSwitch 6850 Series
IEEE 802.1s Multiple Spanning Tree Protocol
(MSTP)
The Alcatel-Lucent Multiple Spanning Tree (MST) implementation provides support for the IEEE
802.1s Multiple Spanning Tree Protocol (MSTP). In addition to the 802.1D Spanning Tree Algorithm
and Protocol (STP) and the 802.1w Rapid Spanning Tree Algorithm and Protocol (RSTP), MSTP also
ensures that there is always only one data path between any two switches for a given Spanning Tree
instance to prevent network loops.
MSTP is an enhancement to the 802.1Q Common Spanning Tree (CST), which is provided when an
Alcatel-Lucent switch is running in the flat Spanning Tree operating mode. The flat mode applies a
single spanning tree instance across all VLAN port connections on a switch. MSTP allows the
configuration of Multiple Spanning Tree Instances (MSTIs) in addition to the CST instance. Each
MSTI is mapped to a set of VLANs. As a result, flat mode can support the forwarding of VLAN traffic
over separate data paths. In addition to 802.1s MSTP support, the 802.1D STP and 802.1w RSTP are
still available in either the flat or 1x1 mode. However, if using 802.1D or 802.1w in the flat mode, the
single spanning tree instance per switch algorithm applies.
MST Specifications:
IEEE Standards supported:
• 802.1D–Media Access Control (MAC) Bridges
• 802.1w–Rapid Reconfiguration (802.1D Amendment 2)
• 802.1Q–Virtual Bridged Local Area Networks
• 802.1s–Multiple Spanning Trees (802.1Q Amendment 3)
Spanning Tree Operating Modes supported:
• Flat mode - one spanning tree instance per switch
• 1x1 mode - one spanning tree instance per VLAN
Spanning Tree Protocols supported:
• 802.1D Standard Spanning Tree Algorithm and Protocol (STP)
• 802.1w Rapid Spanning Tree Algorithm and Protocol (RSTP)
• 802.1s Multiple Spanning Tree Algorithm and Protocol (MSTP)
Spanning Tree Port Eligibility:
• Fixed ports (non-mobile)
• 802.1Q tagged ports
• Link aggregate of ports
Number of 1x1 Spanning Tree instances supported: 253
Number of Multiple Spanning Tree Instances (MSTI) supported:
• 16 MSTI in addition to the Common and Internal Spanning
• Tree instance (also referred to as MSTI 0).
CLI Command Prefix Recognition: All Spanning Tree commands support prefix recognition.
Static (OmniChannel) Link Aggregation 4.3.7 Alcatel-Lucent’s link aggregation software allows you to configure the following two different types
of link aggregation groups:
• Static (OmniChannel) link aggregate groups
• IEEE 802.3ad Dynamic link aggregate groups
Static Link aggregation allows you to combine 2, 4, or 8, physical connections into large virtual
connections known as link aggregation groups. You can create up to 32 link aggregation groups on a
standalone switch.
You can create Virtual LANs (VLANs), configure Quality of Service (QoS) conditions, 802.1Q framing, and
other networking features on link aggregation groups because the switch’s software treats these
Virtual links just like physical links.
Load balancing for Layer 2 non-IP packets is on a MAC address basis and for IP packets the balancing
algorithm uses IP address as well. Ports must be the same speed within the same link aggregate group.
Using link aggregation can provide the following benefits:
• Scalability: You can configure up to 32 link aggregation groups that can consist of 2, 4, or 8
10Mbps, 100Mbps, 1Gbps, or 10Gbps Ethernet links in the switch.
• Reliability: If one of the physical links in a link aggregate group goes down (unless it is the last one)
the link aggregate group can still operate.
• Ease of Migration: Link aggregation can ease the transition from a 100 Mbps Ethernet backbones to
Gigabit Ethernet backbones.
Static Link Aggregation Specifications:
Maximum number of link aggregation groups per switch: 32
Number of Links per group supported: 2,4, or 8
Range for optional group name: 1 to 225 characters
Note: Link aggregation traps include one that will send a trap when a single link in the aggregate group
is down or cannot join the aggregate group.