Westermo RedFox Series - Manual (Page 309)

Westermo OS Management Guide
Version 4.17.0-0
14.2 FRNT and RSTP coexistence
With WeOS it is possible to run FRNT and RSTP on the same switch, be it with
some topology restrictions. Fig.
14.3 shows an example of such a configuration,
where two of the switches in the FRNT ring (thick lines) are running RSTP on the
”non-FRNT” ports.
Switch
RSTP
Switch
RSTP
Switch
RSTP
Switch
FRNT/
RSTP
Switch
FRNT/
RSTP
Switch
RSTP
Switch
FRNT
Switch
RSTP
Switch
FRNT
Loop
handled
by RSTP Loop
handled
by RSTP
Switch
RSTP
Loop
handled
by FRNT
Figure 14.3: Example of coexistence of FRNT and RSTP.
As both RSTP and FRNT want to control a port’s state (FORWARDING/BLOCKING),
only one of the protocols may be activated on each port to avoid protocol con-
flicts. Therefore, if both FRNT and RSTP are configured to operate on a certain
port, FRNT will have precedence to control the port’s state.
Warning
FRNT and RSTP are each able to handle loops within their respective do-
mains, however, if a physical loop is created including some links controlled
by RSTP and others by FRNT, a broadcast storm is likely to occur, since nei-
ther RSTP nor FRNT is able to discover the loop, see fig.
14.4 . Thus, if RSTP
and FRNT is mixed in the same layer-2 network, the operator must ensure
that loops across RSTP and FRNT links never occur.
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