Allied Telesis AlliedWare Plus Operating System Version 5.4.4C (x310-26FT,x310-26FP,x310-50FT,x310-50FP) - Manual (Page 1524)

EPSR Introduction and Configuration
Software Reference for x310 Series Switches
57.42 AlliedWare Plus TM Operating System - Version 5.4.4C C613-50046-01 REV A
EPSR and Spanning Tree Operation
EPSR and the Spanning Tree protocol (STP) address data loop prevention, although they
do it differently. EPSR is manually configured to explicitly identify which links are broken in
the defined ring, whereas STP/RSTP calculates where to break links based on user-
provided values (metrics) that are compared to determine the “best” (or lowest cost) paths
for data traffic.
At the practical level you can use these two techniques to create complementary hybrid
EPSR /STP configurations. This configuration might have a high speed fiber loop topology
backbone-controlled and managed using EPSR. Lobes could extend out from each loop
node into a user mesh network. Any loops in this mesh network would be controlled and
managed using STP/RSTP. Note that EPSR and STP cannot share the same ports.
The following figure shows a basic combined EPSR / STP network.
Figure 57-19: EPSR and spanning tree operation
Data
VLAN
Data VLAN
Data VLAN
Master
Node
Other
Ports
Other
Ports
Other
Ports
Other
Ports
Other
Ports
Control VLAN (control_ring)
Transit
Node
Transit
Node
Transit
Node
EPSR 5.eps
Data VLAN
Port 1.0.1
Primary Port 1.0.2
Secondary
Port 1.0.1
Port 1.0.1 Port 1.0.1
Port 2 Port 2
P S
Node 1
Node 2
Node 3
Node 4
Port 1.0.2
Port 1.0.4 Port 1.0.3
Co
nt
ro
l V
LA
N
D
at
a
V
LA
N
Con
tro
l V
LA
N
D
at
a V
LA
N
EPSR Ring
STP/RSTP
Network