another setting that has impact in the relay behind NAT scenario is the parameter:
_BESGather_Mirror_SiteVersionPollingPeriod
It’s value is, by default 30 minutes. This is the time interval between two consecutive checks of the site version on the parent relay. Let me clarify this concept.
Every time a client asks for a new site to the relay, the relay should in theory check with parent if a new site version exists. This setting controls how often the relay performs this check: if it is set to 30 minutes, the child relay waits 30 minutes before checking with the parent relay if a new site version is available, even if clients are continuously pinging it to check for new site versions.
Usually this setting is not very relevant: if the parent gathers a new site version, it notifies the child relays, that immediately gather the new site version (no need to wait any time). But because in a NAT environment the notifications are blocked, this parameter becomes relevant and prevents a relay from checking more often than every “_BESGather_Mirror_SiteVersionPollingPeriod” minutes if the parent has a site update.
Reducing the value of this setting in the child relay configuration allows to checking more frequently if a site update is available on the parent relay (again in case of pings not reaching the child relay). But decreasing it too much can have negative effects on the performances of the parent relay, which gets pinged too often.