What is the difference between Node, Pool Member, Pool and Virtual Server?

--> Load Balancer is a device which shares application or network traffic across multiple servers.

--> Load Balancer is also called an Application Delivery Controller ( ADC).

--> Load Balancers are divided into two types

i) Layer 4 Load Balancers --- Which works on network and transport layer protocols ( IP, TCP, FTP, UDP).

ii) Layer 7 Load Balancers --- Which works on  Application Layer Protocols ( HTTP/HTTPS).

--> Most Popular load balancer vendors are F5, Citrix , A10, Barracuda, kemp etc.

BIG IP F5 Load Balancer Terminology 

Node:

--> Node is the physical server that will receive traffic from the Load Balancer (Ex: 192.168.1.1).

--> Node is recognized by an IP Address.

--> A node can be part of multiple Pools in F5 LTM with different Service Ports.

--> Nodes can be created manually going to the NODE tab or automatically when you create pool members.


Pool Member:

--> Pool Member is IP Address + Service of Physical Server ( Ex: 192.168.1.1:80).

--> Pool Members are added to Pools for load balancing.

--> We can add the same pool member in the different Pools.



Pool: 

--> A pool is a logical group of pool members which receives and processes traffic for the particular virtual server.

--> Load balancing is performed across pool members depending upon the algorithm being used.

--> Traffic will be forwarded to Pool member in the pool based upon the status of health monitor and load balancing algorithm.

--> Pool can be added to Virtual Server using two methods.

1) Default Pool option in Virtual Server

2) Using Irule or Local Traffic Policy.


Virtual Server:

--> Virtual Server is an IP Address of Load Balancer which is representing a collection of pool members.

--> Each Virtual Server is uniquely identified by using an IP address and Port Number.

--> Virtual Server can be configured in two ways:

1) Host Virtual Server: Listens for Specific IP address

2) Network Virtual Server: Listens for Network address


Reference: F5 Website

Md.Kareemoddin

CCIE# 54759