Brocade Virtual ADX Server Load Balancing Guide (Supporting ADX v03.1.00) - Manual (Page 75)

Brocade Virtual ADX Server Load Balancing Guide 59
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Configuring Direct Server Return
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Enabling L2 DSR on TCP/UDP ports
To configure the Brocade Virtual ADX for L2 DSR, you must enable the feature for individual
TCP/UDP ports when configuring the virtual server.
For example, when you enable TCP port 80 (HTTP) on a virtual server, you can add the DSR
parameter to enable L2 DSR for that port.
Virtual ADX(config)#server virtual-name-or-ip v1 10.157.22.1
Virtual ADX(config-vs-v1)#port 80 dsr
Traffic for other ports still returns through the Brocade Virtual ADX. The Brocade Virtual ADX does
not translate the destination IP address in client requests for the port with L2 DSR enabled.
However, the Brocade Virtual ADX still translates the destination IP address in the client’s request
to the real server’s IP address for other ports.
Syntax: [no] port tcp/udp-port dsr
Configuring the loopback address on a real server
To configure the real servers for L2 DSR, configure a loopback interface on each real server and
assign the VIP addresses to the loopback interface.
The loopback interface enables the real server to respond to client requests directed at the VIPs,
while at the same time keeping the real server “hidden”. The loopback interface responds to
unicast traffic directed to it, but does not respond to ARP requests. The Brocade Virtual ADX
responds to pings and ARPs for the VIPs. Thus, any attempt to obtain the real server’s MAC address
using ARP protocol does not succeed.
You can configure loopback addresses on some common types of real servers. Refer to the
“Server-specific Loopback Configurations” on page 349 for details.
Health checks with L2 DSR
Normally, the Brocade Virtual ADX can perform health checks on an application port only when a
server replies from that port pass back through the Brocade Virtual ADX. If the Brocade Virtual ADX
does not see the real server’s responses to client requests, the Brocade Virtual ADX concludes that
the application or the entire server is down and stops sending client requests to that server.
When you enable an application port for DSR, the Brocade Virtual ADX can still perform heath
checks on the application by sending the health checks to the loopback address you configure on
the real server.
You can use Layer 4 and Layer 7 health checks in your DSR configuration.
• The Brocade Virtual ADX addresses Layer 3 (IP ping) health checks to the real server IP
address.
• The Brocade Virtual ADX addresses Layer 4 and Layer 7 health checks to the real server MAC
address and to the loopback address that matches the VIP address.
The configuration procedures for the health checks are the same as for other types of SLB. Refer to
Chapter 4, “Health Checks” .