The Hitless upgrade and reload feature provide a facility to perform system upgrades or reloads with sub-second traffic loss using non-stop forwarding.

The Hitless upgrade is a variant of ISSU for single CPU systems and does not expect hardware level redundancy to perform upgrade and reload processes without impacting traffic

For more information on upgrading the system and installing packages, see System Setup and Software Installation Guide for Cisco NCS 5000 Series Routers.

• Zero-Packet Loss Using Non-Stop Forwarding - When you perform an upgrade or reload using Hitless method, the hardware state is maintained intact and no hardware components are reset. After the upgrade or reload process, the control plane recovers the old hardware state, performs a reconciliation process with hardware and resumes with normal operations. Both upgrade or reload procedures complete with sub-second traffic loss.

• Support for Reload and Upgrade - The Hitless feature provides support to reload or upgrade the system. If you are performing a reload, you can either upgrade the forwarding container or the entire IOS XR system.

• Graceful Restart of BGP and OSPF in single CPU systems therefore removing the need to have redundancy.

• Non-stop forwarding leading to minimal down time during reload or upgrade process.

• Ability to hold the port state and optics in UP state during reload.

• Ability to maintain LLDP sessions during reload.

The Hitless reload and upgrade feature is only supported on NCS 5011 routers starting from IOS XR release 6.5.x.

Hitless upgrade will lead to traffic loss in the following scenarios:

• In case of an FPGA upgrade the router must be power booted and therefore it will lead to traffic loss and topology loss.

• In case of an upgrade, if Broadcom SDK does not support migration from older version, then it will lead to system reinitialization.

• If the router configuration differs from the combination specified in the Supported Features section.

For more information on upgrading the system and the installing packages, see System Setup and Software Installation Guide for Cisco NCS 5000 Series Routers.

To perform a system upgrade using hitless method, use the following command from Sysadmin prompt:

sysadmin-vm:0_RP0# install activate warm idoperation-id

For more information on upgrading the system and installing packages, see System Setup and Software Installation Guide for Cisco NCS 5000 Series Routers.

You can choose to either perform hitless reload of the forwarding container or of the entire IOS XR system.

For more information on upgrading the system and installing packages, see System Setup and Software Installation Guide for Cisco NCS 5000 Series Routers.