consul-join can help figure out which IPs to use to join consul agents to servers. It respects two ENV variables related to joining.

Simple join with one IP:

JOINIP=10.0.0.1 consul-join
# will exec: consul agent -join=10.0.0.1

Join by looking up registered A records:

JOINDNS=example.com consul-join
# assuming example.com has 2 A records of 10.0.0.1 and 10.0.0.2, then
# will exec: consul agent -join=10.0.0.1 -join=10.0.0.2

Passes all following arguments to consul:

consul-join -config-dir=/config
# will exec: consul agent -config-dir=/config

Also supports -server and will respect the BOOTSTRAP_EXPECT ENV varaible (which it defaults to 3 if missing).

JOINDNS=example.com consul-join -server
# will exec: consul agent -join=10.0.0.1 -join=10.0.0.2 -bootstrap-expect=3 -server

We are considering adding a JOINURL and a related consul-join-server to provide a simple alternative to DNS for keeping track of consul server ips (similar to discovery.etcd.io).