F5 and its gateway

Hi davidy2001 , 
        Of course there is a known direction of traffic. 
> Lets have " L 3 Switch --- F5 --- Nodes " scenario : 
- L3 switch direct its traffic to F5 because there is a " Route " specified on L3 Switch , this Route works as below :
( If you want to reach to a virtual server hosted by F5 , send or throw the traffic on F5 self ip (next hop in routing ) "where F5 self ip and switch are connected and have ips in same subnet") 
- After That F5 will Process coming traffic and deliver this traffic to its internal nodes. 
 
> Lets have " F5 , Or nodes " lunch the process of traffic : 
- For F5 lunches traffic to L3 Switch , to lunch traffic to Switch " let we say  F5 needs to get updates from internet , so it must go through L3 Switch first , by creating a default route on F5 it self , this route says " if F5 want to send any traffic to its next hop and it will be L3 Switch interface in our Example) 

- For Internal Nodes  , you first need to create new Virtual server on F5 to server Nodes traffic , in Case Nodes itself lunch traffic first , it must find a virtual server on F5 recieve its traffic. 
This Virtual server Can be standard , or another type of Virtual servers is widely used for nodes if it want to reach to internet for updates " this type of Virtual servers called " Forwarding ip ". 

- you know that nodes as a servers need to Configure a default gateway , to get out through it .

> Simply , Routing is main controller For Traffic direction or Flow , For F5 or Switch , both of  devices get out based on its routes 
> That was the traffic Flow from F5 perspective. 

Thanks and hopfully it helps you. 
Regards