heartbeat心脏跳的不是太好，请名医指点一二

请问这两句话是具体作什么的呢？

multicast是发给谁？又是做什么用的呢？

那个eth1的位置，应该是写做什么用的interface呢？

我的实验环境里，master和backup是用串口线连接的，
还需要这2个参数吗？

谢谢！

附：
ha-log：（最新一次启动的log）
heartbeat[2321]: 2006/04/26_13:21:49 WARN: Traditional compression selected. Realtime behavior will likely be impacted(!)
heartbeat[2321]: 2006/04/26_13:21:49 info: See http://linux-ha.org/ha.cf/TraditionalCompressionDirective for more information.
heartbeat[2321]: 2006/04/26_13:21:49 WARN: Logging daemon is disabled --enabling logging daemon is recommended
heartbeat[2321]: 2006/04/26_13:21:49 info: **************************
heartbeat[2321]: 2006/04/26_13:21:49 info: Configuration validated. Starting heartbeat 2.0.4
heartbeat[2333]: 2006/04/26_13:21:49 info: heartbeat: version 2.0.4
heartbeat[2333]: 2006/04/26_13:21:52 info: Heartbeat generation: 16
heartbeat[2333]: 2006/04/26_13:21:52 info: G_main_add_TriggerHandler: Added signal manual handler
heartbeat[2333]: 2006/04/26_13:21:52 info: G_main_add_TriggerHandler: Added signal manual handler
heartbeat[2333]: 2006/04/26_13:21:57 info: Removing /var/run/heartbeat/rsctmp failed, recreating.
heartbeat[2333]: 2006/04/26_13:21:59 info: glib: Starting serial heartbeat on tty /dev/ttyS0 (19200 baud)
heartbeat[2333]: 2006/04/26_13:21:59 info: G_main_add_SignalHandler: Added signal handler for signal 17
heartbeat[2333]: 2006/04/26_13:22:02 info: Local status now set to: 'up'
heartbeat[2333]: 2006/04/26_13:22:02 info: Exiting write_hostcachedata process 2557 returned rc 0.

authkeys文件内容：
auth 3
3 md5 AreYouAlive?

haresources文件内容：
localhost.realserver1 \
LVSSyncDaemonSwap::master \
IPaddr2::172.31.0.16/24/eth0

（172.31.0.16是我的VIP）

ha.cf文件内容：
debugfile /var/log/ha-debug
logfile /var/log/ha-log
logfacility local0
keepalive 2
deadtime 30
warntime 10
initdead 120
udpport 694
baud 19200
serial /dev/ttyS0
auto_failback on
node localhost.realserver1
node localhsot.realserver2