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Barracuda Load Balancer ADC

Deploying DSR in a Linux Environment

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To add a non-ARPing adapter to a Real Server running Linux, add an alias to the lo (loopback) adapter. The following commands are examples of how to do this for some versions of Linux. Consult your operating system vendor if you need more details about how to add a non-ARPing loopback adapter.

  1. Edit your rc.local file (usually located at /etc/rc.d/rc.local) and add the following:
    sysctl -w net.ipv4.conf.lo.arp_ignore=1
    sysctl -w net.ipv4.conf.lo.arp_announce=2
    sysctl -w net.ipv4.conf.all.arp_ignore=1
    sysctl -w net.ipv4.conf.all.arp_announce=2
    ifconfig <interface_name> <ip_address> netmask
    -arp up


    <interface_name> is lo:<number> (e.g. lo:0, lo:1, lo:2)
    <ip_address> is the Virtual IP Address for the Service

    For example: 
    ifconfig lo:1 netmask -arp up
  2. httpd.conf must have a VirtualHost entry for the VIPs. Edit the file to add these two lines:
    listen <virtual_ip_address>:80
    listen <real_ip_address>:80


    <virtual_ip_address> is the Virtual IP Address for the Service
    <real_ip_address> is the actual IP Address for the Real Server
  3. To check if the loopback adapter is working, make sure the Real Server is bound to the loopback adapter’s IP address. Output from the ifconfig command should show the presence of the loopback adapter.
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