F5 TCP Health Monitor Send/Receive strings

Hello Adrian,

If its L7 vip, go with http or https monitoring instead of TCP. That will be more recommended that usual port monitoring. if its a L4 vip, use below steps. i have added http monitoring details Aswell(receive and send).

https://my.f5.com/manage/s/article/K01524704  

Steps to Create TCP Health Checks:
Log in to the LTM Device:

Access the LTM device through the command line or GUI.
Create a New TCP Health Monitor:

If using the GUI, navigate to Local Traffic > Monitors > Create.
If using the command line, you can use the tmsh command.
Configure the Monitor Settings:

Name: Assign a name to the monitor (e.g., TCP_Health_Check).
Type: Select TCP.
Send and Receive Strings:
The send and receive strings will depend on the specific application protocol running on the VIP. Here are some common examples:

Example for HTTP VIP:
Send String:

GET / HTTP/1.1\r\nHost: example.com\r\nConnection: close\r\n\r\n
This sends an HTTP GET request to the server.

Receive String:

HTTP/1.1 200 OK
This expects the server to respond with a 200 OK status.

Example for a Simple TCP Echo Server:
Send String:

HELLO
This sends a simple string HELLO to the server.

Receive String:

HELLO
This expects the server to echo back the same string HELLO.

Example Configuration in tmsh:
Here’s how you might configure a TCP health monitor with tmsh:

sh

tmsh create ltm monitor tcp TCP_Health_Check send "GET / HTTP/1.1\r\nHost: example.com\r\nConnection: close\r\n\r\n" recv "HTTP/1.1 200 OK"
Applying the Monitor to a Pool:
After creating the monitor, you need to assign it to the relevant pool:

sh

tmsh modify ltm pool my_pool monitors add { TCP_Health_Check }
Verifying the Configuration:
To ensure your monitor is working correctly, you can check the status:

sh

tmsh show ltm pool my_pool
This will show the status of the pool members and whether they are marked up or down based on the health checks.