Single Spanning Tree - Foundry Networks Switch and Router Installation And Configuration Manual

• You cannot add a subset of the ports in a trunk group to the Fast Uplink Span group. All ports in a trunk group
have the same Fast Uplink Span property, as they do for other port properties.
• If the working trunk group is partially down but not completely down, no switch-over to the backup occurs.
This behavior is the same as in the standard STP feature.
• If the working trunk group is completely down, a backup trunk group can go through an accelerated transition
only if the following are true:
• The trunk group is included in the fast uplink group.
• All other ports except those in this trunk group are either disabled or blocked. The accelerated transition
applies to all ports in this trunk group.
• When the original working trunk group comes back (partially or fully), the transition back to the original
topology is accelerated if the conditions listed above are met.
Configuring a Fast Uplink Port Group
To enable Fast Uplink, use one of the following methods.
USING THE CLI
To configure a group of ports for Fast Uplink Span, enter the following commands:
BigIron(config)# fast uplink-span ethernet 4/1 to 4/4
BigIron(config)# write memory
Syntax: [no] fast uplink-span [ethernet <portnum> [ethernet <portnum>... | to <portnum>]]
This example configures four ports, 4/1 – 4/4, as a Fast Uplink Span group. In this example, all four ports are
connected to a wiring closet switch. Only one of the links is expected to be active at any time. The other links are
redundant. For example, if the link on port 4/1 is the active link on the wiring closet switch but becomes
unavailable, one of the other links takes over. Because the ports are configured in a Fast Uplink Span group, the
STP convergence takes about four seconds instead of taking 30 seconds or longer using the standard STP
forward delay.
If you add a port that is the primary port of a trunk group, all ports in the trunk group become members of the Fast
Uplink Span group.
You can add ports to a Fast Uplink Span group by entering the fast uplink-span command additional times with
additional ports. The device can have only one Fast Uplink Span group, so all the ports you identify as Fast Uplink
Span ports are members of the same group.
To remove a Fast Uplink Span group or to remove individual ports from a group, use "no" in front of the
appropriate fast uplink-span command. For example, to remove ports 4/3 and 4/4 from the Fast Uplink Span
group configured above, enter the following commands:
BigIron(config)# no fast uplink-span ethernet 4/3 to 4/4
BigIron(config)# write memory
If you delete a port that is the primary port of a trunk group, all ports in the trunk group are removed from the Fast
Uplink Span group.
USING THE WEB MANAGEMENT INTERFACE
You cannot configure the Fast Uplink Span feature using the Web management interface.

Single Spanning Tree

By default, each port-based VLAN on a Foundry device runs a separate spanning tree, which you can enable or
disable on an individual VLAN basis.
Alternatively, you can configure a Foundry device to run a single spanning tree across all ports and VLANs on the
device. The single STP feature is especially useful for connecting a Foundry device to third-party devices that run
a single spanning tree in accordance with the 802.1q specification.
Single-instance STP uses the same parameters, with the same value ranges and defaults, as the default STP
support on Foundry devices. See "STP Parameters and Defaults" on page 12-2.
December 2000
Configuring Spanning Tree Protocol (STP) and IronSpan
12 - 19