Administrator Guide

Interoperate with Non-Dell Networking OS Bridges
Dell Networking OS supports only one MSTP region.
A region is a combination of three unique qualities:
• Name is a mnemonic string you assign to the region. The default region name on Dell Networking OS is null.
• Revision is a 2-byte number. The default revision number on Dell Networking OS is 0.
• VLAN-to-instance mapping is the placement of a VLAN in an MSTI.
For a bridge to be in the same MSTP region as another, all three of these qualities must match exactly. The default values for name and
revision match on all Dell Networking OS equipment. If you have non-Dell Networking OS equipment that participates in MSTP, ensure
these values match on all the equipment.
NOTE: Some non-Dell Networking OS equipment may implement a non-null default region name. SFTOS, for example, uses the
Bridge ID, while others may use a MAC address.
Modifying Global Parameters
The root bridge sets the values for forward-delay, hello-time, max-age, and max-hops and overwrites the values set on other MSTP
bridges.
• Forward-delay — the amount of time an interface waits in the Listening state and the Learning state before it transitions to the
Forwarding state.
• Hello-time — the time interval in which the bridge sends MSTP bridge protocol data units (BPDUs).
• Max-age — the length of time the bridge maintains conguration information before it refreshes that information by recomputing the
MST topology.
• Max-hops — the maximum number of hops a BPDU can travel before a receiving switch discards it.
NOTE
: Dell Networking recommends that only experienced network administrators change MSTP parameters. Poorly planned
modication of MSTP parameters can negatively aect network performance.
To change the MSTP parameters, use the following commands on the root bridge.
1 Change the forward-delay parameter.
PROTOCOL MSTP mode
forward-delay seconds
The range is from 4 to 30.
The default is 15 seconds.
2 Change the hello-time parameter.
PROTOCOL MSTP mode
hello-time seconds
NOTE
: With large congurations (especially those congurations with more ports) Dell Networking recommends
increasing the hello-time.
The range is from 1 to 10.
The default is 2 seconds.
3 Change the max-age parameter.
PROTOCOL MSTP mode
max-age seconds
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Multiple Spanning Tree Protocol (MSTP)