using udpu

corosync.conf

# Please read the corosync.conf.5 manual page
compatibility: whitetank

aisexec {
        user:        root
        group:       root
}

service {
        name: pacemaker
        ver: 0
}

totem {
	version: 2

	# secauth: Enable mutual node authentication. If you choose to
	# enable this ("on"), then do remember to create a shared
	# secret with "corosync-keygen".
	secauth: off

	threads: 0

	# interface: define at least one interface to communicate
	# over. If you define more than one interface stanza, you must
	# also set rrp_mode.
	interface {
                member {
                        memberaddr: 172.31.15.101
                }
                member {
                        memberaddr: 172.31.27.99
                }
                # Rings must be consecutively numbered, starting at 0.
		ringnumber: 0
		# This is normally the *network* address of the
		# interface to bind to. This ensures that you can use
		# identical instances of this configuration file
		# across all your cluster nodes, without having to
		# modify this option.
		bindnetaddr: 172.31.15.101
		# However, if you have multiple physical network
		# interfaces configured for the same subnet, then the
		# network address alone is not sufficient to identify
		# the interface Corosync should bind to. In that case,
		# configure the *host* address of the interface
		# instead:
		# bindnetaddr: 192.168.1.1
		# When selecting a multicast address, consider RFC
		# 2365 (which, among other things, specifies that
		# 239.255.x.x addresses are left to the discretion of
		# the network administrator). Do not reuse multicast
		# addresses across multiple Corosync clusters sharing
		# the same network.
		#mcastaddr: 239.255.1.1
		# Corosync uses the port you specify here for UDP
		# messaging, and also the immediately preceding
		# port. Thus if you set this to 5405, Corosync sends
		# messages over UDP ports 5405 and 5404.
		mcastport: 5405
		# Time-to-live for cluster communication packets. The
		# number of hops (routers) that this ring will allow
		# itself to pass. Note that multicast routing must be
		# specifically enabled on most network routers.
		ttl: 1
	}
        transport: udpu
}

logging {
	# Log the source file and line where messages are being
	# generated. When in doubt, leave off. Potentially useful for
	# debugging.
	fileline: off
	# Log to standard error. When in doubt, set to no. Useful when
	# running in the foreground (when invoking "corosync -f")
	to_stderr: no
	# Log to a log file. When set to "no", the "logfile" option
	# must not be set.
	to_logfile: yes
	logfile: /var/log/cluster/corosync.log
	# Log to the system log daemon. When in doubt, set to yes.
	to_syslog: yes
	# Log debug messages (very verbose). When in doubt, leave off.
	debug: off
	# Log messages with time stamps. When in doubt, set to on
	# (unless you are only logging to syslog, where double
	# timestamps can be annoying).
	timestamp: on
	logger_subsys {
		subsys: AMF
		debug: off
	}
}

With multicast must be used udp, but not udpu transport.