Reference: https://www.cnblogs.com/hqjy/p/7615439.html
Introduction keepalived
keepalived observe its name shows, remain viable, which is to keep the network online, and
Also known as hot standby or high availability, which cluster management software and services to ensure a highly available cluster,
Functions like a heartbeat, to prevent single point of failure (single point of failure is a failure that occurs once the means will cause the entire system architecture unusable) occurs .
Speaking keepalived VRRP protocol would have to say, it can be said that the agreement is implemented keepalived basis, so first we take a look at VRRP protocol.
VRRP protocol describes
learned a network of friends all know, when the network design must take into account the redundant disaster recovery, including line redundancy, equipment redundancy to prevent single point of failure in the network, it is implemented in a router or Layer 3 switches at redundancy is particularly important.
In the network there is a protocol to do it, and this is the VRRP protocol, to achieve coincidence occurs Keepalived is high availability (HA) using the VRRP.
VRRP stands for Virtual Router Redundancy Protocol, or virtual routing redundancy protocol. For VRRP, need to know is clear:
1) VRRP is used to implement router redundancy protocol.
2) VRRP backup mode protocol is a protocol of the network in order to eliminate static routing environment default router single point of failure caused by the failure of the design,
May not affect the internal and external data communication and is designed such that failure of the device when the switching function, the parameters do not need to modify the network of the internal network.
3) VRRP backup IP protocol required to have priority routing, routers reduce unnecessary communications.
4) VRRP protocol virtual device into two or more routers a device, provide external virtual router IP (one or more).
However, within the routers group, if actually owning the IP router if the external work, then, is the master, or elected by the algorithm,
MASTER IP router for the virtual realization of various network functions, such as ARP requests, ICMP, etc., and forwarding data, the other device does not have the IP, the state is BACKUP.
In addition to the received VRRP MASTER state advertisement information, the external network does not perform the function, when the primary fails, the BACKUP MASTER will take over the original network functions.
5) When the VRRP protocol configuration, the configuration of each router needs to route a virtual ID (VRID) and a priority value, using grouping VRID router, the router having the same value for the same VRID group,
VRID is a whole number from 0-255; the same group to elect MASTER router by using the priority values. , Who is a big priority MASTER, priority is a positive integer of 0-255.