Configuring Vlan Bridge Hello Time; Configuring Vlan Bridge Max Age Time - Alcatel OmniSwitch 6624 Network Configuration Manual

Configuring STP VLAN Parameters
If the switch is running in the 1x1 Spanning Tree mode, then a priority value is assigned to each VLAN.
When a VLAN is created, STP is enabled and the VLAN bridge priority defaults to 32768. If the switch is
running in the flat Spanning Tree mode, the priority is assigned to VLAN 1.
To change the VLAN bridge priority, enter bridge followed by an existing VLAN ID (or VLAN 1 if using
a flat Spanning Tree instance) then priority followed by a numerical value between 0 and 65535. For
example, the following command changes the priority for VLAN 455 to 25590:
-> bridge 455 priority 25590
To view the VLAN bridge priority value, use the
this command, see the OmniSwitch CLI Reference Guide.

Configuring VLAN Bridge Hello Time

The VLAN bridge hello time interval is the number of seconds a bridge will wait between transmissions of
Configuration BPDU. When a bridge is attempting to become the root or if it has become the root or a
designated bridge, it sends Configuration BPDU out all forwarding ports once every hello time value.
The hello time propagated in a root bridge Configuration BPDU is the value used by all other bridges in
the tree for their own hello time. Therefore, if this value is changed for the root bridge (VLAN), all other
VLANs associated with the same STP instance will adopt this value as well.
If the switch is running in the 1x1 Spanning Tree mode, then a hello time value is defined for each VLAN.
When a VLAN is created, STP is enabled and the hello time defaults to 2 seconds. If the switch is running
in the flat Spanning Tree mode, then a hello time value is defined for VLAN 1. Lowering the hello time
interval improves the robustness of the Spanning Tree topology. However, increasing the hello time inter-
val reduces Spanning Tree overhead.
To change the VLAN bridge hello time, enter bridge followed by an existing VLAN ID (or VLAN 1 if
using a flat Spanning Tree instance) then hello time followed by a numerical value between 1 and 10 to
specify the number of seconds. For example, the following command changes the hello time value for
VLAN 455 to 5 seconds:
-> bridge 455 hello time 5
To view the VLAN bridge hello time value, use the
this command, see the OmniSwitch CLI Reference Guide.

Configuring VLAN Bridge Max Age Time

The VLAN bridge max age time specifies how long, in seconds, the bridge retains Spanning Tree informa-
tion it receives from Configuration BPDU. When a bridge receives a BPDU, it updates its configuration
information and the max age timer is reset. If the max age timer expires before the next BPDU is received,
the bridge will attempt to become the root, designated bridge, or change its root port.
The max age time propagated in a root bridge Configuration BPDU is the value used by all other bridges
in the tree for their own max age time. Therefore, if this value is changed for the root bridge (VLAN), all
other VLANs associated with the same STP instance will adopt this value as well.
If the switch is running in the 1x1 Spanning Tree mode, then a max age time value is defined for each
VLAN. When a VLAN is created, STP is enabled and the max age time defaults to 20 seconds. If the
switch is running in the flat Spanning Tree mode, then the max age value is defined for VLAN 1. Specify-
ing a low max age time may cause STP to reconfigure the topology more often.
page 5-12
show spantree command. For more information about
show spantree
OmniSwitch 6624/6648 Network Configuration Guide
Configuring Spanning Tree Parameters
command. For more information about
April 2004