Users Guide
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 specied 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 rst
• 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.
Failure and Event Logging
Dell Networking systems provide multiple options for logging failures and events.
Trace Log
To track the execution of a program, developers interlace messages with software code.
These messages are called trace messages and are primarily used for debugging and to provide lower-level information than event
messages, which system administrators use. Dell Networking OS retains trace messages for hardware and software and stores them in les
(logs) on the internal ash.
• Trace Log — contains trace messages that relate to software and hardware events, state, and errors. Trace Logs are stored in internal
ash under the directory TRACE_LOG_DIR.
• Crash Log — contains trace messages that relate to IPC and IRC timeouts and task crashes on linecards and are stored under the
directory CRASH_LOG_DIR.
High Availability (HA)
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