Dell Force10 E1200i FTOS Version 8.4.1.5 Configuration Guide for ExaScale - Page 384
Hitless Behavior, Graceful Restart, e c s
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www.dell.com | support.dell.com Hitless Behavior c e Hitless Behavior is supported only on platform: Hitless behavior is supported on E-Series ExaScale ex with FTOS 8.2.1.0. and later. Hitless is a protocol-based system behavior that makes an RPM failover on the local system transparent to remote systems. The system synchronizes protocol information on the standby and primary RPMs such that, the event of an RPM failover, there is no need to notify remote systems of a local state change. Hitless behavior is defined in the context of an RPM failover only and does not include line card, SFM, and power module failures. • On the E-Series: Failovers triggered by software exception, hardware exception, forced failover via the CLI, and manual removal of the primary RPM are all hitless. • On the C-Series: Only failovers via the CLI are hitless. The system is not hitless in any other scenario. Hitless protocols are compatible with other hitless and graceful restart protocols. For example, if hitless OSPF is configured over hitless LACP LAGs, both features work seamlessly to deliver a hitless OSPF-LACP result. However, if hitless behavior involves multiple protocols, all must be hitless in order to achieve a hitless end result. For example, if OSPF is hitless but BFD is not, OSPF operates hitlessly and BFD flaps upon an RPM failover. The following protocols are hitless: • Link Aggregation Control Protocol. Refer to Configure LACP as Hitless. • Spanning Tree Protocol. Refer to Configuring Spanning Trees as Hitless. • On the E-Series only, Bi-directional Forwarding Detection (line card ports). Refer to Bidirectional Forwarding Detection. Graceful Restart e c s Graceful Restart is supported on platform: Graceful restart (also called non-stop forwarding) is a protocol-based mechanism that preserves the forwarding table of the restarting router and its neighbors for a specified period to minimize the loss of packets. A graceful-restart router does not immediately assume that a neighbor is permanently down and so does not trigger a topology change. On E-Series, when you configure graceful restart, the system drops no packets during an RPM failover for protocol-relevant destinations in the forwarding table, and is therefore called "hitless". On the C-Series and S-Series, packet loss is non-zero, but trivial, and so is still called hitless. FTOS supports graceful restart for the following protocols: • Border Gateway Protocol. Refer to Enable graceful restart. • Open Shortest Path First. Refer toGraceful Restart. • Protocol Independent Multicast-Sparse Mode. Refer toPIM-SM Graceful Restart. • Intermediate System to Intermediate System. Refer toIntermediate System to Intermediate System. 384 | High Availability
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