Dell PowerConnect 7024F User Manual - Page 165
NSF and the Storage Access Network, renews its IP address lease with the DHCP server.
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Page 165 highlights
If a host is in the middle of an exchange with the DHCP server when the failover occurs, the exchange is interrupted while the control plane restarts. When DHCP snooping is enabled, the hardware traps all DHCP packets to the CPU. The control plane drops these packets during the restart. The DHCP client and server retransmit their DHCP messages until the control plane has resumed operation and messages get through. Thus, DHCP snooping does not miss any new bindings during a failover. As DHCP snooping applies its checkpointed DHCP bindings, IPSG confirms the existence of the bindings with the hardware by reinstalling its source IP address filters. If Dynamic ARP Inspection is enabled on the access switch, the hardware traps ARP packets to the CPU on untrusted ports. During a restart, the control plane drops ARP packets. Thus, new traffic sessions may be briefly delayed until after the control plane restarts. If IPSG is enabled and a DHCP binding is not checkpointed to the backup unit before the failover, that host will not be able to send data packets until it renews its IP address lease with the DHCP server. NSF and the Storage Access Network Figure 8-15 illustrates a stack of three PowerConnect switches connecting two servers (iSCSI initiators) to a disk array (iSCSI targets). There are two iSCSI connections as follows: Session A: 10.1.1.10 to 10.1.1.3 Session B: 10.1.1.11 to 10.1.1.1 An iSCSI application running on the Management Unit (the top unit in the diagram) has installed priority filters to ensure that iSCSI traffic that is part of these two sessions receives priority treatment when forwarded in hardware. Managing a Switch Stack 165
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1,202
-
1,203
-
1,204
-
1,205
-
1,206
-
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