The key F5 BIG-IP traffic management logical constructs for the BIG-IP DNS and/or LTM are:
- Pool - Pools are logical sets of devices that are grouped together to receive and process traffic. Pools are used to efficiently distribute load across grouped server resources.
- Virtual server - Virtual servers are a traffic-management object that is represented in the BIG-IP system by a destination IP address and service port. Virtual servers require one or more pools.
- Virtual address - A virtual address is an IP address associated with a virtual server, commonly referred to as a VIP (virtual IP). In the BIG-IP system virtual addresses are generally created by the BIG-IP system when a virtual server is created. Many virtual servers can share the same IP address.
- Node - A BIG-IP node is a logical object on the BIG-IP system that identifies the IP address or a fully- qualified domain name (FQDN) of a server that hosts applications. Nodes can be created explicitly or automatically when a pool member is added to a load balancing pool.
- Pool member - A pool member is a service on a node and is designated by an IP address and service (port).
- Monitor - Monitors are pre-configured (system provided) or user created associations with a node, pool, or pool member to determine availability and performance levels. Health or performance monitors check status on an ongoing basis, at a set interval. Monitors allow intelligent decision making by BIG-IP LTM to direct traffic away from unavailable or unresponsive nodes, pools, or pool members. Multiple monitors can be associated with a node, pool, or pool member.
- Data Center - BIG-IP DNS only. All of the BIG-IP DNS resources are associated with a data center. BIG-IP DNS consolidates the paths and metrics data collected from the servers, virtual servers, and links in the data center. BIG-IP DNS uses that data to conduct load balancing and route client requests to the best-performing resource.
- Wide IP (WIP) - BIG-IP DNS only. Wide IP addresses (WIP) are one of the main BIG-IP DNS configuration elements. WIP are identified by a fully qualified domain name (FQDN). Each WIP is configured with one or more pools (global). The global pool members are LTM-hosted virtual servers. BIG-IP DNS servers act as an authority for the FQDN WIP and return the IP address of the selected LTM virtual server to use.
- Listener - BIG-IP DNS only. A listener is a specialized virtual server that passively checks for DNS packets on port 53 and the IP address assigned to the listener. When a DNS query is sent to the IP address of the listener, BIG-IP DNS either handles the request locally or forwards the request to the appropriate resource.
- Probe - BIG-IP DNS only. A probe is an action taken by a BIG-IP system to acquire data from other network resources.
Figure 3 below shows the relationships between applications, virtual servers, pools, pool members (ECS node services), and health monitors.
Figure 3. Relationships between LTM, applications, virtual servers, pools, pool members and health monitors
Figure 4 below shows the BIG-IP Wide IP (FQDN) to global pool member (LTM/site/virtual server) association.
Figure 4. BIG-IP Wide IP (FQDN) to global pool member (LTM/site/virtual server) association