Load balancing & high availability for Linux¶
Keepalived is a routing software written in C. It brings simple and robust load balancing and high availability to Linux systems and Linux based infrastructures, and it runs in production across data centers, ISPs and hardware vendors worldwide.
What is Keepalived?¶
Keepalived builds load balancing on top of the well known Linux Virtual Server (IPVS) kernel module, which delivers Layer 4 load balancing. On top of IPVS, Keepalived runs a set of health checkers that watch each server pool and decide, in real time, whether a real server stays in the topology or drops out according to its health.
High availability comes from the VRRP protocol, the fundamental brick for router failover. Keepalived adds a set of hooks to the VRRP finite state machine so it can react with low level, high speed protocol interactions. To detect network failures as fast as possible it also implements BFD, and a VRRP state transition can take a BFD hint into account to drive a fast failover.
Each framework works on its own or together with the others, so you can build exactly the resilient infrastructure you need.
Three frameworks, one daemon¶
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High availability (VRRP)
A full implementation of VRRP v2 and v3 for IPv4 and IPv6, with sync groups that keep routing paths consistent after a takeover, plus IPSEC-AH securing of protocol adverts.
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Load balancing (LVS/IPVS)
Layer 4 load balancing driven by the kernel IPVS module, configured and maintained from a single place, with several scheduling algorithms and forwarding methods.
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Health checking & BFD
Layer 4 to Layer 7 checkers add and remove real servers automatically, while BFD detects link and peer failures in milliseconds to trigger fast VRRP transitions.
License¶
Keepalived is free software. You can redistribute it and modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 2 of the License, or any later version.