Administrator Guide

When you disable a port channel, all interfaces within the port channel are operationally down also.
Load Balancing Through Port Channels
Dell EMC Networking OS uses hash algorithms for distributing traffic evenly over channel members in a port channel (LAG).
The hash algorithm distributes traffic among Equal Cost Multi-path (ECMP) paths and LAG members. The distribution is based
on a flow, except for packet-based hashing. A flow is identified by the hash and is assigned to one link. In packet-based hashing,
a single flow can be distributed on the LAG and uses one link.
Packet based hashing is used to load balance traffic across a port-channel based on the IP Identifier field within the packet.
Load balancing uses source and destination packet information to get the greatest advantage of resources by distributing traffic
over multiple paths when transferring data to a destination.
Dell EMC Networking OS allows you to modify the hashing algorithms used for flows and for fragments. The load-balance and
hash-algorithm commands are available for modifying the distribution algorithms.
Load-Balancing Method
By default, LAG hashing uses the source IP, destination IP, source transmission control protocol (TCP)/user datagram protocol
(UDP) port, and destination TCP/UDP port for hash computation. For packets without a Layer 3 header, Dell EMC Networking
OS automatically uses load-balance mac source-dest-mac.
Do not configure IP hashing or MAC hashing at the same time. If you configure an IP and MAC hashing scheme at the same
time, the MAC hashing scheme takes precedence over the IP hashing scheme.
To change the IP traffic load-balancing default, use the following command.
● Replace the default IP 4-tuple method of balancing traffic over a port channel.
CONFIGURATION mode
[no] load-balance {ip-selection [dest-ip | source-ip]} | {mac [dest-mac | source-dest-mac
| source-mac]} | {tcp-udp enable} {ipv6-selection} {tunnel}| {ingress-port}
You can select one, two, or all three of the following basic hash methods:
○ ip-selection [dest-ip | source-ip] — Distribute IP traffic based on the IP destination or source address.
○ mac [dest-mac | source-dest-mac | source-mac] — Distribute IPV4 traffic based on the destination or
source MAC address, or both, along with the VLAN, Ethertype, source module ID and source port ID.
○ tcp-udp enable — Distribute traffic based on the TCP/UDP source and destination ports.
○ ingress-port — Option to Source Port Id for ECMP/ LAG hashing.
○ ipv6-selection— Set the IPV6 key fields to use in hash computation.
○ tunnel— Set the tunnel key fields to use in hash computation.
Changing the Hash Algorithm
The load-balance command selects the hash criteria applied to port channels.
If you do not obtain even distribution with the load-balance command, you can use the hash-algorithm command to
select the hash scheme for LAG, ECMP and NH-ECMP. You can rotate or shift the 12–bit Lag Hash until the desired hash is
achieved.
The nh-ecmp option allows you to change the hash value for recursive ECMP routes independently of non-recursive ECMP
routes. This option provides for better traffic distribution over available equal cost links that involve a recursive next hop lookup.
To change to another algorithm, use the second command.
● Change the default (0) to another algorithm and apply it to ECMP, LAG hashing, or a particular line card.
CONFIGURATION mode
hash-algorithm {algorithm-number | {ecmp {crc16 | crc16cc | crc32MSB | crc32LSB | crc-
upper | dest-ip | lsb | xor1 | xor2 | xor4 | xor8 | xor16} [number] hg {crc16 | crc16cc
| crc32MSB | crc32LSB | xor1 | xor2 | xor4 | xor8 | xor16} stack-unit stack-unit-number |
380
Interfaces