Configuration

High Availability: Network of Virtual Services

This topology provides a highly available service with minimal hardware requirements. See the overview. for information on how this setup works.

The documentation that follows assumes that all nodes on the network are set up with correct interfaces and routes for each network they are connected to as per the diagram above. The default route for the real-servers is assumed to be the router, but may be an alternate route if available.

This example builds on the example of a high availability single virtual service and adds the ability to have RFC 1519 [offsite], CIDR networks of virtual addresses. The configuration steps for the single virtual service are required in addition to the configuration below.

• Network Preparation For this configuration to work any gateway routers on the network need to route traffic for the virtual services network, 192.168.0.0/24 via the virtual address, 192.168.7.240. Details on configuring this for a router running Debian or Red Hat Enterprise Linux follow.

  • Common to Debian and Red Hat Enterprise Linux

    IPV4 forwarding must be enabled. This is done by adding configuration of net.ipv4.ip_forward to /etc/sysctl.conf as follows:

    # Enables packet forwarding
    net.ipv4.ip_forward = 1
    

    For these changes to take effect the sysctl command may be used:

    /sbin/sysctl -p
    net.ipv4.ip_forward = 1
    

  • Specific to Red Hat Enterprise Linux

    To route 192.168.0.0/24 to 192.168.6.240, add an entry to /etc/sysconfig/static-routes.

    
    any net 192.168.0.0 netmask 255.255.255.0 gw 192.168.6.240
    
    

    Restarting networking on the machine will make this change take effect.

    
    /etc/init.d/network restart
    Shutting down interface eth0:               [  OK  ]
    Setting network parameters:                 [  OK  ]
    Bringing up interface lo:                   [  OK  ]
    Bringing up interface eth0:                 [  OK  ]
    
    

    You can verify that this worked using the ip command.

    
    /sbin/ip route list 192.168.0.0/24
    192.168.0.0/24 via 192.168.6.240 dev eth0 
    
    

  • Specific to Debian

    To route 192.168.0.0/24 to 192.168.6.240, add up and pre-down lines to lines to the entry in /etc/network/interfaces for the interface that is connected to the Real-Servers. A sample entry for eth0 follows:

    
    auto eth0
    iface eth0 inet static
       address 192.168.6.1
       netmask 255.255.255.0
       up ip route add 192.168.0.0/24 via 192.168.6.240
       pre-down ip route del 192.168.0.0/24 via 192.168.6.240
    	       
    

    Restarting networking on the machine will make this change take effect.

    
    /etc/init.d/networking restart
    Reconfiguring network interfaces... done.
    
    

    You can verify that this worked using the ip command.

    
    /sbin/ip route list 192.168.0.0/24
    192.168.0.0/24 via 192.168.6.240 dev eth0 
    
    

• Real-Servers

  The Real-Servers should be set up as per high availability single virtual service, with the exception that the haresources file is updated to include the following resource:

  IPaddr2::192.168.6.240/24/eth0/192.168.6.255
  

  This ensures that the real-server will accept traffic for all of 192.168.0.0/24 as local. This updated /etc/ha.d/haresources file includes this change. To effect the change, restart heartbeat on both real-servers.

  /etc/init.d/heartbeat restart
  

  After a few moments heartbeat should add the virtual addresses to eth0 and lo on the master. This can be verified using the ip command. output has been truncated show only the eth0 interface. You can verify that came up using the ip command. The following output has been truncated to only show information for lo:0.

  
  /sbin/ip addr sh
  1: lo: >LOOPBACK,UP< mtu 16436 qdisc noqueue 
      link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
      inet 127.0.0.1/8 brd 127.255.255.255 scope host lo
      inet 192.168.0.0/24 brd 192.168.0.255 scope global lo
  3: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
      link/ether 00:50:56:4f:30:07 brd ff:ff:ff:ff:ff:ff
      inet 192.168.6.4/16 brd 192.168.6.255 scope global eth0
      inet 192.168.6.240/16 brd 192.168.6.255 scope global secondary eth0
  
  

  Note: The netmask of 255.255.255.0 on the lo:0 interface indicates that this interface will accept traffic for all of the addresses in network 192.168.0.0 netmask 255.255.255.0. This behaviour is peculiar to the loopback interface (lo) and aliases.

Copyright © 2000-2005, Horms
Last Updated: Sat Mar 4 16:33:56 2006 +0900

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