Problems of Tomcat Session Clustering

Today, I tryied to session clustering between two tomcat servers, reading cluster-howto document for tomcat-6.0.

My system is as below:

Server1: (HTTPD + tomcat1)
Server2: (only tomcat2 w/o HTTPD)

    Apache HTTPD
        /          \
      /              \
 tomcat1      tomcat2

However, I'm not familiar with web programs, so it was difficult and spent a lot of time. (-_-;;) But, I finally succeed in configuring. There was some problems with firewall settings and route configurations. I'd like to share them with you.

1) firewall settings

Check that multicast port is on your UDP open list and the receiver TCP port is also for both machines open! I added below list to iptables.

-A RH-Firewall-1-INPUT -p udp --dport 45564 -d 228.0.0.4 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp --dport 4000 -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 4000 -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 45564 -j ACCEPT

2) network interface for multicast

# route add -host 228.0.0.4 dev eth0
# netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
228.0.0.4       0.0.0.0         255.255.255.255 UH        0 0          0 eth0
192.168.123.0   0.0.0.0         255.255.255.0   U         0 0          0 eth0
169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 eth0
0.0.0.0         192.168.123.254 0.0.0.0         UG        0 0          0 eth0