Users Guide

For example, if you configure hitless open shortest path first (OSPF) over hitless the link aggregation
control protocol (LACP) link aggregation groups (LAGs), both features work seamlessly to deliver a hitless
OSPF-LACP result. However, to achieve a hitless result, if the hitless behavior involves multiple protocols,
all protocols must be hitless. For example, if OSPF is hitless but bidirectional forwarding detection (BFD) is
not, OSPF operates in hitless mode and BFD flaps upon a control-plane failover.
The following protocols are hitless:
• 802.1X (802.1X)
• Bidirectional Forwarding Detection (Bidirectional Forwarding Detection (BFD))
• Internet Group Management Protocol (Internet Group Management Protocol (IGMP) and IGMP
Snooping)
• Link aggregation control protocol (Link Aggregation Control Protocol (LACP))
• Link layer discovery protocol (Link Layer Discovery Protocol (LLDP))
• Spanning tree protocol (Spanning Tree Protocol (STP))
Graceful Restart
Graceful restart (also known as 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.
Dell Networking OS supports graceful restart for the following protocols:
• Border gateway protocol
• Open shortest path first
• Protocol independent multicast — sparse mode
• Intermediate system to intermediate system
Software Resiliency
During normal operations, the Dell Networking OS monitors the health of both hardware and software
components in the background to identify potential failures, even before these failures manifest.
System Health Monitoring
The Dell Networking OS also monitors the overall health of the system.
Key parameters such as CPU utilization, free memory, and error counters (for example, CRC failures and
packet loss) are measured, and after exceeding a threshold are used to initiate recovery mechanism.
High Availability (HA)
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