Explains how CPSS version changes introduced in Cisco IOS XR Release 26.1.1 affect UDC traffic during software upgrades, downgrades, and Disaster Recovery operations, detailing the conditions and expected disruption periods.
Cisco IOS XR Release 26.1.1 introduces a new version of the CPSS, which manages the internal control Ethernet switch on the Route Processor (RP). When the software version crosses R26.1.1 either through an upgrade from an earlier release or a downgrade back to one, the CPSS version changes as well. This event triggers a reset and reinitialization of the internal Ethernet switch, temporarily interrupting UDC traffic.
UDC traffic disruption during software upgrade or downgrade
When Cisco IOS XR Release 26.1.1 or later is installed on these platforms, or when downgrading from this release, expect this behavior.
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UDC traffic is interrupted for about 100 seconds.
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The disruption begins during the Post Bootup FPD upgrade phase of the boot sequence.
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Traffic recovers automatically when the link comes back up without any user action.
The system reports a SWITCH_FIRMWARE_BOOT_FAIL syslog and triggers a switch reset.
Operations that do not cause UDC traffic disruption
Certain operations do not change the CPSS version and do not disrupt UDC traffic. These operations include:
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RP warm reload
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Line card warm reload
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ESD or CMA process restart
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OLT or ILA FPD upgrade
Disaster Recovery considerations
During Disaster Recovery, the Route Processor is physically replaced. If the replacement RP has a different CPSS version, the switch resets, disrupting UDC traffic. The disruption duration depends on the BIOS version of the replacement RP.
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BIOS version 5.90 or later: UDC traffic disruption lasts about 100 seconds.
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BIOS version earlier than 5.90: UDC traffic disruption lasts about 32 minutes due to an extra switch reset cycle.
Before performing Disaster Recovery with RP replacement, verify that the replacement RP has BIOS version 5.90 or later. Using an RP with an older BIOS extends UDC traffic disruption from 100 seconds to 32 minutes.
Verify UDC port traffic statistics
Use this procedure to verify that UDC ports are operational and traffic is flowing after a software upgrade or downgrade by using switch statistics commands on NCS 1010, NCS 1014, and NCS 1020.