User manual

(Rapid) Spanning Tree
6874_en_09 PHOENIX CONTACT 5-5
Figure 5-4 (R)STP Configuration
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 5-18 on page 5-24 and Figure 5-19 on page 5-25 as an
example for 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.