I have a site running on 4 different servers , when the database is located in one of those servers...

Recently started a strange problem
The site ran well for a few hours and then three servers can not connect to the SQL data center
Could I think this is limited or freight.
the central server include the site continues to work, and browse the site normally when you log on through this server
There are kind of limiting external servers
But also difficult to say what the limit, that the checkpoint, several hours after it returns to work.


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And I'll add more information seems to me vital,
Most likely this is not setting any SQL
I did several experiments with connections between the servers 3306 (details of the mysql)
When I try to connect to a different server, I got an error message such as:
"4.1.21-standard`€")Ipz58W,¢.|J[pC=E%'ÿBad handshake"

That is, there is a connection. Can I open a connection
But when I try to connect to the server on which sits the main server SQL, then nothing gets.