Brocade Virtual ADX Server Load Balancing Guide (Supporting ADX v03.1.00) User Manual
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Brocade Virtual ADX Server Load Balancing Guide
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Layer 4 health checks
4
•
UDP health check – The Brocade Virtual ADX sends a UDP packet with garbage (meaningless)
data to the UDP port:
-
If the server responds with an ICMP “Port Unreachable” message, the Brocade Virtual ADX
concludes that the port is not alive.
-
If the server does not respond at all, the Brocade Virtual ADX assumes that the port is alive
and received the garbage data. Because UDP is a connectionless protocol, the Brocade
Virtual ADX and other clients do not expect replies to data sent to a UDP port, so a lack of
response indicates a healthy port.
NOTE
The Brocade Virtual ADX assumes that a port is a UDP port unless you configure the port as a TCP
port. To configure a port as a TCP port, add a port profile for the port and specify the port type TCP.
Refer to
“Basing a port’s health on the health of another port”
After the Brocade Virtual ADX sends an initial packet (TCP or UDP) to the server to bring the port up,
the Brocade Virtual ADX waits one second and then checks for a response from the server. If no
response is received during that time, the Brocade Virtual ADX will send another packet. The time
at which the Brocade Virtual ADX sends the second packet depends on the number of ports being
brought up at that time. The Brocade Virtual ADX will send the second packet after it has sent initial
packets to all the other ports being brought up at that time.
By default, the Brocade Virtual ADX does not repeat the Layer 4 health check after bringing up the
port when you bind the real server to the virtual server. However, you can enable a periodic
keepalive health check for the port. To configure the keepalive health check globally, configure a
port profile for the port. You also can enable or disable the keepalive health check on individual
real servers.
The following Layer 4 health check types are supported:
•
TCP
•
UDP