Flex Hash and Optimized Boot-UpThis chapter describes the Flex Hash and fast-boot enhancements.Topics:• Flex Hash Capability Overview• Configuring the Flex Hash Mechanism• Configuring Fast Boot and LACP Fast Switchover• Optimizing the Boot Time• Interoperation of Applications with Fast Boot and System States• RDMA Over Converged Ethernet (RoCE) Overview• Preserving 802.1Q VLAN Tag Value for Lite SubinterfacesFlex Hash Capability OverviewThe flex hash functionality enables you to configure a packet search key and matches packets based on the search key. When a packetmatches the search key, two 16-bit hash fields are extracted from the start of the L4 header and provided as inputs (bins 2 and 3) forRTAG7 hash computation. You must specify the offset of hash fields from the start of the L4 header, which contains a flow identificationfield.You can configure the system to include the fields present at the offsets that you define (from the start of the L4 header) as a part of LAGand ECMP computation. Also, you can specify whether the IPv4 or IPv6 packets must be operated with the Flex Hash mechanism.Keep the following points in mind when you configure the flex hash capability:• A maximum of eight flex hash entries is supported.• A maximum of 4 bytes can be extracted from the start of the L4 header.• The offset range is 0 – 30 bytes from the start of the L4 header.• Flex hash uses the RTAG7 bins 2 and 3 (overlay bins). These bins must be enabled for flex hash to be configured.• If you configure flex hash by using the load-balance ingress-port enable and the load-balance flexhashcommands, the show ip flow and show port-channel-flow commands are not operational. Flex hash settings and theseshow commands are mutually exclusive; only one of these capabilities can be functional at a time.Configuring the Flex Hash MechanismThe flex hash functionality enables you to configure a packet search key and matches packets based on the search key. When a packetmatches the search key, two 16-bit hash fields are extracted from the start of the L4 header and provided as inputs (bins 2 and 3) forRTAG7 hash computation. You must specify the offset of hash fields from the start of the L4 header, which contains a flow identificationfield.1 In Dell Networking OS Release 9.3(0.0), you can enable bins 2 and 3 by using the load-balance ingress-port enablecommand in Global Configuration mode. To configure the flex hash functionality, you must enable these bins.CONFIGURATION modeDell(conf)# load-balance ingress-port enable15Flex Hash and Optimized Boot-Up 315
