White Papers

Table Of Contents
The user will need to configure the boot-type to warmboot under the reload-type configuration mode. Warmboot is a system
reload technique where the NPU will not restart. Only the CPU is restarted to bring up the upgraded software. Software
upgrade ISSU, is the typical use case for warmboot. Since BCM chip is already up and running while the software is restarted,
there should not be any traffic outage during warmboot. However, since the CPU is restarted during the warmboot process,
control plane traffic drop will be observed and the same would resume post warmboot.
Mirroring flow control packets
ISSU for mirroring flow control packets is a graceful implementation . The mirror ACL FP rules and the MTPs would be cleared
out when the box comes up in warmboot during the ISSU audit phase, and the flows are re-programmed again with mirror action
when the mirroring configurations are downloaded. In case of legacy L3 ACL based mirroring , the mirroring actions would be
cleared out and re-programmed while the FP rules are retained.
PFC
This feature has been designed to ensure that there is no traffic loss with respect to PFC during warmboot or upgrade to a
different switch image.
The user will need to configure the boot-type to warmboot under the reload-type configuration mode. All the supported feature
information gets stored in a persistent storage, and when the switch goes in for a reload, all hardware programmed entries will
be saved and traffic will be treated seamlessly, during reload. After the reload is complete, the running-config and startup-config
will be compared and if there is a difference, the device will be programmed based on the startup-config.
QoS
This feature has been designed to ensure that there is no traffic loss with respect to QoS traffic during warmboot or upgrade to
a different switch image.
The user will need to configure the boot-type to warmboot under the reload-type configuration mode. All the supported feature
information gets stored in a persistent storage, and when the switch goes in for a reload, all hardware programmed entries will
be saved and traffic will be treated seamlessly, during reload. After the reload is complete, the running-config and startup-config
will be compared and if there is a difference, the device will be programmed based on the startup-config.
Tunnel Configuration
This feature has been designed to ensure that there is no traffic loss with respect to tunneled traffic during warmboot or
upgrade to a different switch image.
The user will need to configure the boot-type to warmboot under the reload-type configuration mode. All the supported feature
information gets stored in a persistent storage, and when the switch goes in for a reload, all hardware programmed entries in
CAM and FIB will be saved and traffic will be treated seamlessly, during reload. After the reload is complete, the running-config
and startup-config will be compared and if there is a difference, the device will be programmed based on the startup-config. If
tunnel keepalive is configured over the tunnel interface then tunnel keepalive threshold should be set to 90 seconds.
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In-Service Software Upgrade