LACP Distribution Calculator
Check how evenly a LAG hash spreads flows across members and how much skew a non-power-of-two bundle causes.
Inputs
Skew on the Busiest Member
0.130%
Hash Buckets per Member
42
Buckets on the Busiest Member
43
Ideal Share per Member
16.667%
Flows per Member
833
Distribution Verdict
Uneven — 0.13% extra load on 4 member(s); a power-of-two bundle divides cleanly
Step by step
Values used
Active member links = 6 links; Concurrent flows = 5,000 flows; Hash buckets in hardware = 256 buckets; Hash policy = Source + destination IP
LACP Distribution
Buckets per member = floor(buckets ÷ members); the members that absorb the remainder carry one extra bucket, so skew = (busiest buckets ÷ buckets) − (1 ÷ members).
Flow distribution
flows per member = flows ÷ members, assuming uniform hash input.
Skew on the Busiest Member
= 0.130
Hash Buckets per Member
= 42
Buckets on the Busiest Member
= 43
Ideal Share per Member
= 16.667
Flows per Member
= 833
Distribution Verdict
= Uneven — 0.13% extra load on 4 member(s); a power-of-two bundle divides cleanly
How it works
Hashing maps each flow to one of a fixed number of buckets and buckets to members. When the member count divides the bucket table exactly the split is perfect; otherwise the members holding the leftover buckets run hot, which is the real reason bundles are built in powers of two. Bucket skew is small, but hash-entropy skew is not — a few elephant flows or a MAC-only hash behind a router can put most of the traffic on one member while the bundle reports plenty of spare capacity.
Formulas
LACP Distribution
Buckets per member = floor(buckets ÷ members); the members that absorb the remainder carry one extra bucket, so skew = (busiest buckets ÷ buckets) − (1 ÷ members).
- buckets
- Size of the hardware hash table, typically 256 entries
- remainder
- Buckets left over when members do not divide the table evenly
- skew
- Extra share of traffic the busiest member receives
Flow distribution
flows per member = flows ÷ members, assuming uniform hash input.
Frequently Asked Questions
How is LACP Distribution calculated?
Buckets per member = floor(buckets ÷ members); the members that absorb the remainder carry one extra bucket, so skew = (busiest buckets ÷ buckets) − (1 ÷ members). Hashing maps each flow to one of a fixed number of buckets and buckets to members. When the member count divides the bucket table exactly the split is perfect; otherwise the members holding the leftover buckets run hot, which is the real reason bundles are built in powers of two.
Why does LACP Distribution matter?
Bucket skew is small, but hash-entropy skew is not — a few elephant flows or a MAC-only hash behind a router can put most of the traffic on one member while the bundle reports plenty of spare capacity.
What values do I need to enter?
This calculator takes 4 inputs: Active member links, Concurrent flows, Hash buckets in hardware, Hash policy. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.