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Download Allied Telesis AT-8824 Install guide
Transcript
Ethernet Protection Switching Ring (EPSR) 13 EPSR and Spanning Tree Operation EPSR and the Spanning Tree protocols (STP) each address the issue of data loop prevention, although their method of doing so is quite different. For information on STP, see the Spanning Tree Chapter of your switch’s Software Refernce. EPSR is manually configured to explicitly identify which link(s) will be broken in the defined ring, whereas STP/RSTP calculates where to break links based upon user provisioned values (metrics) that are compared to determine the "best" (or lowest cost) paths for data traffic. At the practical level these two techniques can be employed to create complementary hybrid EPSR / STP configurations. Such a configuration might have a high speed fibre loop topology backbone—controlled and managed using EPSR. Lobes could extend out from each loop node into a user mesh network. Any loops existing within this mesh network would be controlled and managed using STP/RSTP. Figure 1-9 on page 1-13 shows a basic combined EPSR / STP network. Figure 1-9: EPSR and Spanning Tree Operation Port 2 Secondary Port 1 Primary Other Ports l tro P Co ntr ol V Node 1 N ta LA Da Master Node N V LA Dat aV LA Co N n S AN VL Transit Node Other Ports Transit Node EPSR Ring Other Ports Node 4 Node 2 Transit Node Port 1 Port 4 Da ta VL AN Node 3 STP/RSTP Network Data VLAN Other Ports Port 2 Control VLAN (control_ring) Port 3 AN VL ta Da Port 1 Port 2 Port 1 Other Ports Port 2 Data VLAN EPSR 5.eps Note that EPSR and STP cannot share the same ports.
