Create a Load Balancing VIP on F5

On an F5 BIG-IP LTM, a VIP (Virtual IP) is typically created as a Virtual Server. 

It listens on a client-facing IP/port and sends traffic to a pool of backend servers.

Traffic flow

Client

HTTPS 10.10.10.100:443
            v
+------------------+
|   F5 BIG-IP LTM  |
|   Virtual Server   |
| 10.10.10.100:443 |
+------------------+

          |

          v

      web_pool

       /     \

      v       v

10.20.20.11  10.20.20.12

Example
Suppose you have:

VIP: 10.10.10.100
Port: 443
Protocol: HTTPS
Pool: web_pool
Backend servers:
10.20.20.11:443
10.20.20.12:443

Using the F5 GUI
Log in to the F5 BIG-IP management interface.
Go to Local Traffic → Virtual Servers → Virtual Server List.
Click Create.

Configure the main settings:
Name: vs_web_https
Destination Address/Mask: 10.10.10.100
Service Port: HTTPS (443)
Protocol: TCP

Under Configuration, select:

HTTP Profile: http if you want F5 to inspect/process HTTP

SSL Profile (Client): your client-side SSL certificate/profile if F5 terminates HTTPS

Source Address Translation: commonly Auto Map if the backend servers don't have a route back through the F5

Under Resources → Default Pool, select your backend pool.

Click Finished.

If you haven't created the pool yet
Go to:

Local Traffic → Pools → Pool List → Create

For example:
Pool Name: web_pool
Members:
10.20.20.11:443
10.20.20.12:443

You should also configure an appropriate health monitor, such as HTTPS or TCP, so F5 knows which members are available.

Using the F5 GUI

Log in to the F5 BIG-IP management interface.
Go to Local Traffic → Virtual Servers → Virtual Server List.
Click Create.

Configure the main settings:
Name: vs_web_https
Destination Address/Mask: 10.10.10.100
Service Port: HTTPS (443)
Protocol: TCP

Under Configuration, select:

HTTP Profile: http if you want F5 to inspect/process HTTP

SSL Profile (Client): your client-side SSL certificate/profile if F5 terminates HTTPS

Source Address Translation: commonly Auto Map if the backend servers don't have a route back through the F5

Under Resources → Default Pool, select your backend pool.

Click Finished.

General Properties

Name: vs_testbluesftp-443
Partition /Path : Common
Type: Performance (Layer 4)
Source Address: Host
                0.0.0.0/0

Destination Address/Mask: Host
                    10.25.246.60


Service Port: 443  Https

Notify Status to Virtual Address: Checked

CREATE A POOL 

If you haven't created the pool yet

Go to:

Local Traffic → Pools → Pool List → Create

For example:
Pool Name: web_pool
Members:
10.20.20.11:443
10.20.20.12:443

You should also configure an appropriate health monitor, such as HTTPS or TCP, so F5 knows which members are available.

Important distinction

If by VIP you mean a floating/self IP or you're working with an F5 HA pair, that's different from creating a Virtual Server. A typical HA setup has Self IPs, floating Self IPs, and Virtual Servers/VIPs.

If you tell me whether you're using F5 BIG-IP TMOS via GUI or CLI, and whether the VIP is HTTP, HTTPS, TCP, or UDP, I can give you the exact configuration steps/CLI commands.