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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