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(Rapid) Spanning Tree
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Figure 5-3 “(R)STP Configuration” web page
Large tree support
If RSTP is operated using the default values, it is suitable for up to seven switches along the
relevant path (see Figure 5-17 on page 130 and Figure 5-18 on page 131 as an example of
the relevant path). The RSTP protocol would therefore be possible in a ring topology for up
to 15 switches.
The “Large Tree Support” option makes the ring topology suitable for 28 switches along the
relevant path if RSTP is used. The “Large Tree Support” option could provide an RSTP ring
topology with up to 57 devices. When using “Large Tree Support”, please note the following:
–
In the large tree support RSTP topology, do not use devices that do not support large
tree support.
– Enable the “Large Tree Support” option on all devices.
– If RSTP is to be activated as the redundancy mechanism in an existing network with
more than seven switches along the relevant path, then the “Large Tree Support” option
must first be enabled on all devices.
– It is recommended that “Large Tree Support” is not activated in networks with less than
seven switches along the relevant path.
Maximum age of STP information
The parameter is set by the root switch and used by all switches in the ring. The parameter
is sent to make sure that each switch in the network has a constant value, against which the
age of the saved configuration is tested.
The “Maximum Age of STP Information”, “Hello Time”, and “Forward Delay” fields have the
same meaning as for STP. These values are used when this switch becomes a root. The
values currently used can be found under “(R)STP General”.
Hello time
Specifies the time interval within which the root bridge regularly reports to the other bridges
via BPDU.