Trunk Groups; Ironspan Stp Enhancements - Foundry Networks Switch and Router Installation And Configuration Manual

Foundry Switch and Router Installation and Configuration Guide
want certain MAC addresses to always be present in the device's Layer 2 address table, you can add them as
static entries.
A static MAC entry, like a cached (dynamic) MAC entry, maps a MAC address to the Foundry device's port
attached to that device.
Unlike cached MAC entries, static MAC entries provide the following benefits:
• You can assign a QoS priority to a static MAC entry.
• You can specify VLAN membership for a static MAC entry.
• A static entry prevents broadcast storms that can be caused when a server's MAC entry is removed. For
example, if the server goes down long enough for the server's entry to age out, the Foundry device sends
packets addressed to the server as broadcasts until the device relearns the cache entry for the server.
You can specify port priority (QoS) and VLAN membership (VLAN ID) for the MAC address. On Layer 2 Switches,
you also can specify the device type (router or host) for the entry.
NOTE: On Foundry routers, you also can create static IP routes, ARP entries, and RARP entries. Foundry Layer
2 Switches support only static MAC addresses.
For more details on configuring static MAC addresses, see "Configuring Static MAC Entries" on page 10-38.
Standard Spanning Tree Protocol (STP)
The Spanning Tree Protocol (STP) is a protocol for detecting and eliminating logical loops in a Layer 2
broadcast domain. STP is described in the IEEE 802.1d bridge protocols standard. STP is supported on all
Foundry switches and routers.
STP also ensures that the device uses the most efficient path when multiple paths exist between ports. Moreover,
if a selected path fails, STP searches for and then establishes an alternate path to prevent or limit retransmission
of data.
STP is disabled by default on routers but is enabled by default on Layer 2 Switches and on the ServerIron.
For information about configuring STP, see "Enabling or Disabling the Spanning Tree Protocol (STP)" on page 10-
34.

IronSpan STP Enhancements

IronSpan is a set of Layer 2 features that extend the operation of standard STP. IronSpan enables you to fine tune
standard STP and avoid some of its limitations. IronSpan includes the following features:
• Fast Port Span – By default, devices running Fast Port Span perform Spanning Tree Protocol (STP)
convergence in four seconds instead of 30 or more seconds for certain ports connected to end stations.
• Fast Uplink Span – Enhances STP by allowing a Foundry device with redundant uplinks to quickly resume
forwarding, in just four seconds. This feature is similar to Fast Port Span but applies to certain inter-switch
links on Foundry devices, instead of Foundry links to end stations.
• Single-instance STP – Runs a single spanning tree on all ports in the Foundry device, even if you have
already configured multiple port-based VLANs on the device.
For more information and configuration procedures, see "Configuring Spanning Tree Protocol (STP) and
IronSpan" on page 12-1.

Trunk Groups

A trunk group is a set of ports that provide a high speed link between two Foundry devices or between a Foundry
device and a server. A trunk group can provide a transfer rate of up to 4 Gbps of bi-directional traffic.
In addition to enabling load sharing of traffic, trunk groups provide redundant, alternate paths for traffic. Thus, if a
link in a trunk group fails, the device still uses the other links in the trunk group.
8 - 16 December 2000