Red Hat LINUX VIRTUAL SERVER 4.7 - ADMINISTRATION Manual

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Red Hat LINUX VIRTUAL SERVER 4.7 - ADMINISTRATION Manual Manual pdf 38 page image

requests for any of the VIPs is the current active LVS node.2. Once this has been completed on each real server, save the ARP table entries by typing thefollowing commands on each real server:service arptables_jf savechkconfig --level 2345 arptables_jf onThe chkconfig command will cause the system to reload the arptables configuration onbootup — before the network is started.3. Configure the virtual IP address on all real servers using ifconfig to create an IP alias. Forexample:# ifconfig eth0:1 192.168.76.24 netmask 255.255.252.0 broadcast192.168.79.255 upOr using the iproute2 utility ip, for example:# ip addr add 192.168.76.24 dev eth0As previously noted, the virtual IP addresses can not be configured to start on boot using theRed Hat system configuration tools. One way to work around this issue is to place thesecommands in /etc/rc.d/rc.local.4. Configure Piranha for Direct Routing. Refer to Chapter 4, Configuring the LVS Routers withPiranha Configuration Tool for more information.2.2. Direct Routing and iptablesYou may also work around the ARP issue using the direct routing method by creating iptablesfirewall rules. To configure direct routing using iptables, you must add rules that create atransparent proxy so that a real server will service packets sent to the VIP address, even thoughthe VIP address does not exist on the system.The iptables method is simpler to configure than the arptables_jf method. This method alsocircumvents the LVS ARP issue entirely, because the virtual IP address(es) only exist on theactive LVS director.However, there are performance issues using the iptables method compared toarptables_jf, as there is overhead in forwarding/masquerading every packet.You also cannot reuse ports using the iptables method. For example, it is not possible to runtwo separate Apache HTTP Server services bound to port 80, because both must bind toChapter 3. Setting Up LVS28