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⚡ Quickstart

This guide shares one virtual IP (VIP) between two hosts. The VIP is held by one node at a time and moves to the other one when that node goes down.

Host Address
Node 1 192.168.1.10
Node 2 192.168.1.11
VIP 192.168.1.231

Requirements

  • The ip_vs kernel module loaded on each host (modprobe ip_vs).
  • Host networking (--network=host), so Keepalived manages the real interface of the host.
  • The NET_ADMIN, NET_RAW and NET_BROADCAST capabilities.

Run Two Nodes

Run one container per host. Only the peer address and the priority change between the two.

docker run --detach --name keepalived \
  --network=host --cap-add=NET_ADMIN --cap-add=NET_RAW --cap-add=NET_BROADCAST \
  --env KEEPALIVED_INTERFACE="eth0" \
  --env KEEPALIVED_VIRTUAL_IPS="192.168.1.231" \
  --env KEEPALIVED_UNICAST_PEERS="192.168.1.11" \
  --env KEEPALIVED_PRIORITY="150" \
  --env KEEPALIVED_PASSWORD="s3cret" \
  osixia/keepalived

docker run --detach --name keepalived \
  --network=host --cap-add=NET_ADMIN --cap-add=NET_RAW --cap-add=NET_BROADCAST \
  --env KEEPALIVED_INTERFACE="eth0" \
  --env KEEPALIVED_VIRTUAL_IPS="192.168.1.231" \
  --env KEEPALIVED_UNICAST_PEERS="192.168.1.10" \
  --env KEEPALIVED_PRIORITY="100" \
  --env KEEPALIVED_PASSWORD="s3cret" \
  osixia/keepalived

services:
  keepalived:
    image: osixia/keepalived
    container_name: keepalived
    network_mode: host
    restart: unless-stopped
    cap_add:
      - NET_ADMIN
      - NET_RAW
      - NET_BROADCAST
    environment:
      KEEPALIVED_INTERFACE: "eth0"
      KEEPALIVED_VIRTUAL_IPS: "192.168.1.231"
      KEEPALIVED_UNICAST_PEERS: "192.168.1.11"
      KEEPALIVED_PRIORITY: "150"
      KEEPALIVED_PASSWORD: "s3cret"

Three things to get right:

  • KEEPALIVED_INTERFACE is the interface name on the host (eth0, ens18, enp2s0...). Check it with ip -br addr.
  • KEEPALIVED_UNICAST_PEERS lists the other nodes only, never the node itself.
  • KEEPALIVED_PASSWORD must be the same on every node. VRRP only uses its first 8 characters.

With several values, separate them with spaces: KEEPALIVED_VIRTUAL_IPS="192.168.1.231 192.168.1.232".

Check That It Works

The node with the highest priority takes the VIP:

docker logs keepalived
# ... INFO    VRRP INSTANCE VI_1 entered MASTER state

ip addr show eth0
# inet 192.168.1.10/24 ...
# inet 192.168.1.231/32 scope global eth0

Stop the container on node 1: within a few seconds node 2 logs entered MASTER state and holds the VIP.

Start node 1 again: it comes back as BACKUP and the VIP stays on node 2. This is intended, see Failback.

Next Steps