Dell PowerConnect 7048P User Manual - Page 167
NSF and Routed Access, the Management Unit.
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NSF and Routed Access Figure 8-16 shows a stack of three units serving as an access router for a set of hosts. Two LAGs connect the stack to two aggregation routers. Each LAG is a member of a VLAN routing interface. The stack has OSPF and PIM adjacencies with each of the aggregation routers. The top unit in the stack is the Management Unit. Figure 8-16. NSF and Routed Access ` LAG1 ` Access Router LAG2 Aggregation Routers If the Management Unit fails, its link to the aggregation router is removed from the LAG. When the control plane restarts, both routing interfaces come back up by virtue of the LAGs coming up. OSPF sends grace LSAs to inform its OSPF neighbors (the aggregation routers) that it is going through a graceful restart. NOTE: The graceful restart feature for OSPF is disabled by default. For information about the web pages and commands to configure NSF for OSPF or OSPFv3, see "Configuring OSPF and OSPFv3" on page 931. The grace LSAs reach the neighbors before they drop their adjacencies with the access router. PIM starts sending hello messages to its neighbors on the aggregation routers using a new generation ID to prompt the neighbors to quickly resend multicast routing information. PIM neighbors recognize the new generation ID and immediately relay the group state back to the restarting router. IGMP sends queries to relearn the hosts' interest in multicast groups. IGMP tells PIM the group membership, and PIM sends Managing a Switch Stack 167
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-
1,207
-
1,208
-
1,209
-
1,210
-
1,211
-
1,212
-
1,213
-
1,214
-
1,215
-
1,216
-
1,217
-
1,218
-
1,219
-
1,220
-
1,221
-
1,222
-
1,223
-
1,224
-
1,225
-
1,226
-
1,227
-
1,228
-
1,229
-
1,230
-
1,231
-
1,232
-
1,233
-
1,234