Service Manual

When you disable a port channel, all interfaces within the port channel are operationally down also.
Load Balancing Through Port Channels
Dell Networking OS uses hash algorithms for distributing trac evenly over channel members in a port channel (LAG).
The hash algorithm distributes trac among Equal Cost Multi-path (ECMP) paths and LAG members. The distribution is based on a
ow, except for packet-based hashing. A ow is identied by the hash and is assigned to one link. In packet-based hashing, a single
ow can be distributed on the LAG and uses one link.
Packet based hashing is used to load balance trac across a port-channel based on the IP Identier eld within the packet. Load
balancing uses source and destination packet information to get the greatest advantage of resources by distributing trac over
multiple paths when transferring data to a destination.
Dell Networking OS allows you to modify the hashing algorithms used for ows and for fragments. The load-balance and hash-
algorithm commands are available for modifying the distribution algorithms.
NOTE: Hash-based load-balancing on multi-protocol label switching (MPLS) does not work when you enable packet-
based hashing (load-balance ip-selection packet-based).
Load-Balancing Method
For LAG hashing on the source IP, destination IP, source transmission control protocol (TCP)/user datagram protocol (UDP) port,
and destination TCP/UDP port are used for hash computation by default. For packets without a Layer 3 header, Dell Networking OS
automatically uses load-balance mac source-dest-mac.
Do not congure IP hashing or MAC hashing at the same time. If you congure 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 trac load-balancing default, use the following command.
• Replace the default IP 4-tuple method of balancing trac 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 trac based on the IP destination or source address.
– mac [dest-mac | source-dest-mac | source-mac] — Distribute IPV4 trac 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 trac 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 elds to use in hash computation.
– tunnel— Set the tunnel key elds 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 trac 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
Interfaces
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