Squid 3.2 - Proper configuration for random outbound IP with a single user authentication?

There is an example in the online docs is for a three way split. Each step takes away a portion of the traffic that gets to that step and not a portion of all traffic.

• Starting with all traffic taking a 1/3 leaves 2/3.
• Take half of 2/3 leaves 1/3
• Take all of the remaining 1/3

Squid-Cache-Wiki: Feature: ACL type "Random"

acl third random 1/3
acl half random 1/2

tcp_outgoing_address x.154.198.x third
tcp_outgoing_address x.154.198.x half
tcp_outgoing_address x.154.198.x

Your config has 1/3, 1/3, 1/3, all which works out to:

• Starting with all take 1/3 leaving 2/3
• Take 1/3 of 2/3 (2/9) leaves 4/9
• Take 1/3 of 4/9 (4/27) leaves 8/27
• Take the remaining 8/27

If your first and fourth outgoing address are the same then it will get 17/27ths of the traffic.