A Virtual IP (VIP) is an IP address not assigned to a specific physical network interface but is used for redundancy, load balancing, or high availability. It allows multiple systems to share a single IP address dynamically.
How Virtual IP Works
- A VIP does not belong to any single device; instead, it is mapped to one of several devices dynamically.
- If the active device fails, the VIP automatically moves to a backup device.
- Users continue accessing services without knowing which physical device is handling their request
Example of Virtual IP in Action
- Scenario: A bank has two web servers behind a VIP (
192.168.1.100). - Users access the bank’s website using
192.168.1.100. - A load balancer distributes traffic between Web Server 1 (
192.168.1.10) and Web Server 2 (192.168.1.11). - If Web Server 1 fails, the VIP shifts traffic to Web Server 2 automatically.
Technologies That Use Virtual IPs
- VRRP (Virtual Router Redundancy Protocol) – Used in routers to provide high availability.
- HSRP (Hot Standby Router Protocol) – Cisco’s proprietary VIP solution for router redundancy.
- Load Balancers (F5, HAProxy, NGINX, AWS ELB) – Use VIPs for distributing traffic among backend servers.
Key Use Cases of Virtual IPs
- High Availability (HA) – If one server/router fails, the VIP can shift to another system without disrupting service (used in HA clusters).
- Load Balancing – Distributes traffic across multiple servers behind a single VIP, improving performance (used in web servers, databases).
- Failover Mechanisms – A backup system takes over when the primary fails (used in firewalls, gateways).
