Every shared web hosting server has Connection Tracking restrictions. This tracking enables to track all connections from a single IP addresses to the server. The tracking counts the total number of connections and if the total number of connections is greater than prescribed value (200 for Host Mayo) then the offending IP address is blocked. It helps to mitigate some type of DOS attacks and even brute forcing.
The con of this option is that if it is set too low there may be some false positive. Thats why we have selected it above the normal range used by other populat hosts like Godaddy, Blue host etc. Read full comparison of our hardware resource with other hosts here.
Some protocols like FTP, IMAPD and HTTP are connection hungry so they can trigger this limit quite easily specially where there are a lot of closed connections in TIME_WAIT. On the contrast, a server that is prone to DOS attacks, limiting connections per ip is quite useful.
A more reasonable setting for this option is around 300 if the server is not commercial.
For commercial server the normal limit is 150 with some hosts going up to 300.
Host Mayo shared web hosting has adopted a moderate choice and has upgraded their connection tracking limit from 150 to 200 just to avoid any false positive.
We use ConfigServer Security & Firewall to track connection. It is a complete firewall solution for CentOS that not only helps in tracking connection but is a full fledged firewall package.
The picture above shows an ip being blocked by the ConfigServer Firewall. The ip had 244 connection and crossed the 150 limit. This happens so fast and server is continuously monitoring connections of all the ips. When the sever detected that a certain ip was above the threshold it blocked the ip permanently and notified us using an email.