Does Big-IP forward layer 4 to pool servers?

Hi JamesCrk , 
How are you , 
I have tested your scenarios on my lab and found 2 different results. 
( My implementation) 
> 2 F5 VEs , one for monitoring whereas the other for publishing virtual servers and serve user data. 

I did my test in two differnet scenarios , I used ( Layer 4 TCP monitor " your demand" and http layer 7 monitor ) 

FOR (Layer 4 TCP monitor ) : 
> I found as long as the virtual server is up on F5 , external monitor is able to open 3 way-handshake with second F5 , but this 3 way handshake connection stopped outside and F5 doesn’t Forward it to backend server. 
> which means that if this virtual server become down for any reason , external monitor will not be able to open a 3 way-handshake with your F5 and it will mark this virtual server as down. 

According that , no TCP traffic related to external monitor forwarded to the backend , it is only between External monitor and F5 from outside. 

FOR ( Layer 7 http monitor ) 
> I have configured a custom http monitor to check periodically for a specific resource on web server. 
> I found Extenal monitor opens ( TCP 3 way handshake first with F5 and send a piece of http traffic " GET /custom_Path " ) to F5 and F5 by its role recieves this traffic and opened a ( TCP 3 way handshake first with F5 and send a piece of http traffic " GET /custom_Path " ) and send it to servers. 
> when server replied by ( 200 OK ) to F5 , F5 sent this responce back to External monitor , and here external monitor marked it as UP/available after getting the specified resource exactly. 

I want to say now , 
Application Layer 7 health monitors from external monitors , F5 deals with these monitors as a users data traffic , take request and give them replay. 
but with Layer 4 health monitors {TCP} , external monitor and F5 opens only ( a tcp 3 way handshake ) with each other if the virtual server is UP on F5 , and no traffic forwarded to web servers  again related to (tcp 3 way handshake ) 

That was my analysis for your case After labing it and do all above test scenarios. 


Regards