Lag Load Distribution - Dell Force10 S2410-01-10GE-24P Configuration Manual

A LAG can offer the following benefits:
• Increased reliability and availability — if one of the physical links in the LAG goes down, traffic will
be dynamically and transparently reassigned to one of the other physical links.
• Better use of physical resources — traffic can be load-balanced across the physical links.
• Increased bandwidth — the aggregated physical links deliver higher bandwidth than each individual
link.
• Incremental increase in bandwidth — A LAG may be used when a physical upgrade would produce a
10-times increase in bandwidth, but only a two- or five-times increase is required.
LAGs:
• Behave like any other Ethernet link to a VLAN
• Are treated as physical ports with the same configuration parameters, spanning tree port priority, path
cost, etc.
• Can be a member of a VLAN: See
Default VLAN, VLAN 1.
• Can have a router port member, but routing will be disabled while it is a member. For information on
LAG routing, see
• Can be comprised of interfaces from different units of an S-Series stack.

LAG Load Distribution

Traffic is distributed (load-balanced) over links in a LAG using a hashing algorithm. Since the
packet-forwarding ASICs differ among the S-Series platforms, the load-balancing algorithm is also
different. Currently, the CLI does not include a command to change the algorithm.
• S50:
IPv4 packets: The hash is based on the eXclusive OR (XOR) of the 3 least significant bits (LSB) of the source
and destination IP addresses.
Non-IP packets: The hash is based on the XOR of the 3 LSBs of the source and destination MAC addresses.
• S50V, S50N, S25P:
IPv4 and IPv6 packets: The hash is based on the XOR of the source IP (v4 or v6) address and Layer 4 port
with the destination IP (v4 or v6) address and Layer 4 port.
Non-IP packets: The hash is based on the source and destination MAC addresses, VLAN, type, ingress ASIC,
and ingress port.
• S2410:
All packets: The hash is based on the source and destination MAC addresses, type, VLAN, VLAN priority, and
ingress port.
On all platforms, MAC addresses must be learned for hashing to work. Broadcast, unknown unicast, and
multicast packets are sent to a single port (the lowest numbered port) in the LAG.
166 | Link Aggregation
VLANs on page
Link Aggregation on page 269
207. However, LAGs cannot be a member of the
in the Routing chapter.