Administrator Guide

RTAG7
RTAG7 is a hashing algorithm that load balances the traffic within a trunk group in a controlled manner. In order to effectively increase the
bandwidth of the LAG/Equal Cost Multiple Path routes, traffic is balanced across the member links. The balancing is performed by using
the RTAG7 hashing, which is designed to have the member links used efficiently as the traffic profile gets more diverse.Hashing-based
load balancing is used in the following applications:
• L3 ECMP
• LAGs
• HiGig trunking
The RTAG7 hash scheme generates a hash that consists of the following two portions:
• The first portion is primarily generated from packet headers to identify micro-flows in the traffic. The Parameters that are considered
for hash computations by default in RTAG7 hashing is shown in the given example:
DellEMC#show load-balance
Load-Balancing Configuration For LAG & ECMP:
--------------------------------------------
IPV4 Load Balancing Enabled
IPV4 FIELDS : source-ipv4 dest-ipv4 vlan protocol L4-source-port L4-dest-port
IPV6 Load Balancing Enabled
IPV6 FIELDS : source-ipv6 dest-ipv6 vlan protocol L4-source-port L4-dest-port
Mac Load Balancing Enabled
MAC FIELDS : source-mac dest-mac vlan ethertype
Load Balancing Configuration for tunnels
ipv4-over-ipv4 Payload header
ipv4-over-ipv6 Payload header
ipv6-over-ipv6 Payload header
ipv6-over-ipv4 Payload header
ipv4-over-gre-ipv4 Payload header
ipv6-over-gre-ipv4 Payload header
ipv4-over-gre-ipv6 Payload header
ipv6-over-gre-ipv6 Payload header
mac-in-mac header based hashing is disabled
TcpUdp Load Balancing Enabled
DellEMC(conf)#
• Packet Header parameters for the first portion of the RTAG7 hash can be controlled. By default, all the listed parameters from the
Packet header are considered for hash computation. Few parameters [on demand] can be removed using the given CLIs.
DellEMC(conf)#load-balance ?
flexhash Enable flexhash based on IP Protocol
ingress-port Option to Source Port Id for ECMP/LAG hashing
ip-selection Set the IPV4 key fields to use in hash computation(default =
source-ip dest-ip vlan protocol L4-source-port L4-dest-port)
ipv6-selection Set the IPV6 key fields to use in hash computation(default =
source-ipv6 dest-ipv6 vlan protocol L4-source-port L4-dest-port)
mac Set the mac key fields to use in hash computation(default = source-
mac dest-mac vlan ethertype)
tcp-udp Option to use TCP/UDP ports in packet for ECMP/LAG hashing
tunnel Set the tunnel key fields to use in hash computation(default =
Hash-computation based on Inner Header)]
• The second portion comes from static physical configuration such as ingress and egress port numbers.
• RTAG7 hashing also provides options to select between multiple hash algorithms that would result in balanced traffic distribution for
various traffic patterns.
DellEMC(conf)#hash-algorithm ecmp ?
crc16 CRC16_BISYNC - 16 bit CRC16-bisync polynomial
crc16cc CRC16_CCITT - 16 bit CRC16 using CRC16-CCITT polynomial
crc32LSB CRC32_LOWER - LSB 16 bits of computed CRC32
crc32MSB CRC32_UPPER - MSB 16 bits of computed CRC32(default)
crc-upper Use Upper 32 bits of key for hash computation
flow-based-hashing Enable flow based hashing
dest-ip Use Destination IP for ECMP hashing
lsb Always return the LSB of the key as the hash
Equal Cost Multi-Path (ECMP)
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