Specifications

26 Barracuda Load Balancer Administrator’s Guide
to a series of switches that eventually reach the WAN port of the Load Balancer without going
through any other machines.
If you specify Route-Path deployment for the Barracuda Load Balancer, but only use Real Servers
with Direct Server Return enabled, the physical LAN port is not used by the Barracuda Load
Balancer, and the LAN adapter may remain undefined in the Web administration interface.
On the
Basic>Services page, each Real Server listed under each Service must individually be
configured for Direct Server Return mode. Click
Edit for each Real Server, and select Enable for the
Direct Server Return option.
Deployment Notes
When deploying Real Servers in Direct Server Return mode, note the following:
• The Barracuda Load Balancer needs to have the WAN adapter plugged into the same switch or
VLAN as all of the Real Servers.
• The WAN IP, all VIPs, and all of the Real Servers that use Direct Server Return must be on the
same IP subnet.
• Each Real Server needs to recognize the VIP as a local address. This requires enabling of a non-
ARPing virtual adapter such as a loopback adapter and binding it to the VIP address of the load-
balanced Service. Because this is not a true adapter, there should be no gateway defined in the
TCP/IP settings for this adapter.
• Real Servers accepting traffic from multiple VIPs must have a loopback adapters enabled for
each VIP. Additionally, the applications on each Real Server must be aware of both the Virtual
IP address as well as the real IP addresses.
Deployment in a Linux Environment
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)
2. Add the following to your rc.local file:
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 255.255.255.255
-arp up
where:
<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:1 192.168.4.217 netmask 255.255.255.255 -arp up
3.
httpd.conf must have a VirtualHost entry for the VIPs. Edit the file to add these two lines: