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PIC Considerations
Take the following PIC restrictions into consideration before
performing a unified ISSU:
- Unsupported PICs—If a PIC is not supported by unified
ISSU, at the beginning of the upgrade the software issues a warning
that the PIC will be brought offline. After the PIC is brought offline
and the ISSU is complete, the PIC is brought back online with the
new firmware.
- PIC combinations—For some PICs, newer JUNOS services
can require significant Internet Processor ASIC memory, and some configuration
rules might limit certain combinations of PICs on particular platforms.
With a unified ISSU:
- If a PIC combination is not supported by the software
version that the router is being upgraded from, the upgrade will be
aborted.
- If a PIC combination is not supported by the software
version to which the router is being upgraded, the in-service software
upgrade will abort, even if the PIC combination is supported by the
software version from which the router is being upgraded.
- Interface statistics—Interface statistics might
be incorrect because:
- During bootup of the new microkernel on the Packet Forwarding
Engine (PFE), host-bound traffic is not handled and might be dropped,
causing packet loss.
- During the hardware update of the Packet Forwarding Engine
and its interfaces, traffic is halted and discarded. (The duration
of the hardware update depends on the number and type of interfaces
and on the router configuration.)
- During a unified ISSU, periodic statistics collection
is halted. If hardware counters saturate or wrap around, the software
does not display accurate interface statistics.
- CIR oversubscription—If oversubscription of committed
rate information (CIR) is configured on logical interfaces:
- And the sum of the CIR exceeds the physical interface's
bandwidth, after a unified in-service software upgrade is performed,
each logical interface might not be given its original CIR.
- And the sum of the delay buffer rate configured on logical
interfaces exceeds the physical interface's bandwidth, after a unified
in-service software upgrade is performed, each logical interface might
not receive its original delay-buffer-rate calculation.
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