Owners Manual

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.
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 files (logs) on the internal flash.
● Trace Log — contains trace messages that relate to software and hardware events, state, and errors. Trace Logs are
stored in internal flash 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.
Core Dumps
A core dump is the contents of RAM a program uses at the time of a software exception and identifies the cause of the
exception.
There are two types of core dumps: application and kernel.
● Kernel core dump — the central component of an OS that manages system processors and memory allocation and makes
these facilities available to applications. A kernel core dump is the contents of the memory the kernel uses at the time of an
exception.
● Application core dump — the contents of the memory allocated to a failed application at the time of an exception.
High Availability (HA)
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