Brocade Virtual ADX Server Load Balancing Guide (Supporting ADX v03.1.00) - Manual (Page 240)

224 Brocade Virtual ADX Server Load Balancing Guide
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Miscellaneous health check settings
4
Syntax: [no] server identify-server-by-ip
Health check of multiple websites on the same real server
If you host multiple websites on the same real server, with each website using a different VIP, you
can perform an independent health check for each VIP.
One method for binding two VIPs to the HTTP port on the same real server, you create an alias for
the HTTP port on one of the VIPs. To create an alias for the HTTP port, you configure the VIP to bind
to an alternate port number on the real server, then disable port translation for that binding. The
Brocade Virtual ADX collects and presents information for the alias port number, but traffic from
both VIPs actually goes to the HTTP port on the real server.
The state of the master port is used for indicating the health of ports aliased to the master port. For
example, if a VIP uses port 81 as an alias for the HTTP port, then the state information reported for
the HTTP port is used as the state information for port 81. If the HTTP port is reported down, then
port 81 is reported down.
When a real server supports multiple websites, tying the alias port's state to the master port's state
can cause incorrect information to be reported. For example, consider a real server hosting VIPs v1
and v2. VIP v1 is bound to the HTTP port on the real server, and VIP v2 uses port 81 as an alias for
the HTTP port. The Layer 7 health check reports state information about the HTTP port. When VIP
v1 is taken down for maintenance, the Layer 7 health check reports that the HTTP port is down.
Because the state information reported for the HTTP port is also used as the state information for
port 81, the Brocade Virtual ADX considers port 81 to be down as well, incorrectly reflecting the
state of VIP v2, which could be functioning normally.
To eliminate this problem, you establish separate health checks for the alias ports. Health checks
for the alias ports will continue to be performed regardless of the HTTP port's status. The following
is an example of this kind of configuration.
Virtual ADX(config)#server virtual-name-or-ip v1 192.168.1.160
Virtual ADX(config-vs-v1)#port http
Virtual ADX(config-vs-v1)#bind http rs32 http
Virtual ADX(config-vs-v1)#exit
Virtual ADX(config)#server virtual-name-or-ip v2 192.168.1.161
Virtual ADX(config-vs-v2)#port http
Virtual ADX(config-vs-v2)#port http use-alias-port-state
Virtual ADX(config-vs-v2)#no port http translate
Virtual ADX(config-vs-v2)#bind http rs32 81
Virtual ADX(config-vs-v2)#exit
Virtual ADX(config)#server real rs32 10.1.1.32
Virtual ADX(config-rs-rs32)#port http
Virtual ADX(config-rs-rs32)#port http keepalive
Virtual ADX(config-rs-rs32)#port http url "HEAD /"
Virtual ADX(config-rs-rs32)#port 81
Virtual ADX(config-rs-rs32)#port 81 keepalive
Virtual ADX(config-rs-rs32)#port 81 url "GET /81keepalive.htm"
Virtual ADX(config-rs-rs32)#exit
In this configuration, two VIPs are bound to a single real server. VIP v2 uses port 81 as an alias for
port 80; information the Brocade Virtual ADX receives about port 81 is attributed to VIP v2. If VIP v1
is taken down for maintenance, the Layer 7 health check done for port 80 fails, and the Brocade
Virtual ADX marks the HTTP port FAILED. However, health checks continue to be performed for port
81. Port 81 (and thus VIP v2) will continue to be reported active as long as it passes its health
check.