Ask the Expert: ASR9000 Hardware Architecture

Question

With Satya Narra and Xander Thuijs 
Welcome to the Cisco Support Community. This is an opportunity to learn and ask questions about software installation, SMU installation, ASR9000 architecture, installing satellite (ASR9000 nv), and troubleshooting of the Cisco ASR 9000 Series Aggregation Services Routers with experts Satya Narra and Xander Thuijs.
The Cisco ASR 9000 Series Aggregation Services Routers product family offers a significant added value compared to the prior generations of carrier Ethernet routing offerings. The Cisco ASR 9000 Series is an operationally simple, future-optimized platform using next-generation hardware and software. 
Satya Narra is a network consulting engineer and specialist in ASR9000 deployments for service provider networks. He is an expert in many technology areas, including IP routing, MPLS, BGP, OSPF, multicast, system architecture, and network design. Satya has a master of science degree in electrical engineering from Wichita State University, Wichita, KS. He started his career as a customer support engineer in TAC/HTTS supporting some of the biggest networks, including Comcast, Citi, Amazon, JPMorgan, AT&T, Vodofone, and others.   
Xander Thuijs is a principal engineer for the Cisco ASR 9000 Series and Cisco IOS-XR product family at Cisco. He is an expert and advisor in many technology areas, including IP routing, WAN, WAN switching, MPLS, multicast, BNG, ISDN, VoIP, Carrier Ethernet, System Architecture, network design and many others. He has more than 20 years of industry experience in carrier Ethernet, carrier routing, and network access technologies. Xander  holds a dual CCIE certification (number 6775) in service provider and voice technologies. He has a master of science degree in electrical engineering from Hogeschool van University in Amsterdam.
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Answer 1

Hi Lisa,
The mLACP switchover method can be modified using the following CLI:
RP/0/0/CPU0:IOSXR(config)#interface bundle-ether 1 mlacp switchover type ?
  brute-force    Force switchover by disabling all local member links
  revertive      Revert based on configured priority values
RP/0/0/CPU0:ios(config)#interface bundle-ether 1 mlacp switchover type
These options(and the default, when this configuration is not present) are mutually exclusive, and the configuration must match on the bundle on both POA's. They determine the dynamic priority manamgement or brute force mechanism is used, and whether the behaviour is revertive or non-revertive.
Dynamic Priority Management
Switchover is acheved gracefully by modifying the LACP port priorites.
Brute force
This does not involve any priority changes. When using brute force, the operational priority always matches the configured priority. A Switchover is performed when the bundle goes down on the active POA. A switchover is also performed, If active-minimum-links is not satisfied, it brings down other active links on this bundle to force a switchover completely to other PoA.
Revertive
You can configure the MC-LAG in Revertive switchover mode. It means, whenever higher priority links are available, it forces an automatic switchover to that PoA.
Non-revertive
By default switchover is non-revertive. It means,  bundle does not fail back to the original active PoA except when a subsequent failure is encountered. In this mode, POA's do not consider to be primary and secondary, only active or standby. The configured priorities are only used to determine which POA is initally active.
Regards,
--SN