Administrator Guide

Link Aggregation 981
undetected and thus cause undesirable network behavior. Both static and
dynamic LAGs (via LACP) can detect physical link failures within the LAG
and continue forwarding traffic through the other connected links within that
same LAG. LACP can also detect switch or port failures that do not result in
loss of link. This provides a more resilient LAG. Best practices suggest using
dynamic link aggregation instead of static link aggregation. When a port is
added to a LAG as a static member, it neither transmits nor receives LACP
PDUs.
What is LAG Hashing?
Dell Networking N-Series switches support configuration of hashing
algorithms for each LAG interface. The hashing algorithm is used to
distribute traffic load among the physical ports of the LAG while preserving
the per-flow packet order. Enhanced hashing mode is the recommended and
default hashing mode for Dell Networking N-Series switches.
The hashing algorithm uses various packet attributes to determine the
outgoing physical port.
The switch supports the following set of packet attributes to be used for hash
computation:
• Source MAC, VLAN, EtherType, and incoming port.
• Destination MAC, VLAN, EtherType, and incoming port.
• Source IP and Source TCP/UDP port numbers.
• Destination IP and Destination TCP/UDP port numbers.
• Source/Destination MAC, VLAN, EtherType, and incoming port.
• Source/Destination IP and Source/Destination TCP/UDP port numbers.
• Enhanced hashing mode
Enhanced hashing mode has following advantages:
• MODULO-N operation based on the number of ports in the LAG.
• Packet attributes selection based on the packet type. For layer-2 packets,
Source and Destination MAC address plus physical source port are used
for hash computation. For IP packets, Source IP, Destination IP address,
TCP/UDP ports, and physical source port are used.
• Non-Unicast traffic and Unicast traffic is hashed using a common hash
algorithm.