Why didn't my LAN balance to ISP2 when upload saturated ISP1?



  • Hi,

    This could be a case of me misunderstanding how multi-wan load balancing works.

    I have a network with 2 ISPs; ISP_1 and ISP_2.  I set up two gateway groups.  GATEWAY_A has ISP_1 as tier 1 and ISP_2 as tier 2.  GATEWAY_B has ISP_2 as tier 1 and ISP_1 as tier 2.

    I also have two LANs; LAN_A uses GATEWAY_ALAN_B uses GATEWAY_B.  My intent was to have LAN_A tending to use ISP_1 and LAN_B tending to use ISP_2 because LAN_A is a lot of download type traffic and ISP_1 is 2.5x faster than ISP_2.  Please feel free to point out any errors in this logic.

    However, today I had a machine that saturated the upstream bandwidth to ISP_1, but LAN_A continued to (try to) use GATEWAY_A instead of balancing over to GATEWAY_B.  The description for gateway selection says:

    If all links in a priority level are exhausted we will use the next available link(s) in the next priority level.

    I interpreted that as (ex:) selecting a tier 2 link if all the tier 1 links are saturated.  Did I misinterpret what it does?  Does it actually mean tier 2 links will only be used when all tier 1 links are completely unavailable?  I use member down detection, so even though ISP_1 was pinned, it wasn't flagged as being down.

    Thanks for any help.



  • Those words are misleading IMHO - substitute "down" for "exhausted" and that is what it does.
    You Load Balance by putting multiple gateways at the same tier. Then new connections get allocated around the gateways of the same tier (that are up) in the gateway group.
    For Failover, put gateways at different tiers and the Tier 1 will be used exclusively first, then when all Tier 1 are down Tier 2 is used…
    As you imply, it might also be nice to use a Tier 1 gateway, and when it appears to be saturated with traffic, then put new connections onto a Tier 2 gateway... - there is no functionality to do that.
    If you have multiple Tier1 gateways of different bandwidths, then you can put different weights in the gateway advanced parameters to make the system allocate more/less client connection to particular gateways (rather than just even balancing).


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