Brocade Virtual ADX Global Server Load Balancing Guide (Supporting ADX v03.1.00) - Manual (Page 90)

80 Brocade Virtual ADX Global Server Load Balancing Guide
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Enabling DNS request logging
1
This configuration can be made locally on the individual site ADX device. If health status reporting
interval is also configured globally on the GSLB Brocade Virtual ADX, then the health status interval
configuration on the individual site ADX device takes precedence over it for that site ADX device.
Note that if health status configuration is done neither globally on the GSLB Brocade Virtual ADX
nor locally on an individual site ADX device, then the site ADX device reports the health status
information to the GSLB Brocade Virtual ADX at default interval – i.e. every 5 seconds.
Debugging the distributed health check
You can debug the distributed health check feature on the GSLB controller Brocade Virtual ADX by
entering the debug distributed-hcheck command on the GSLB controller Brocade Virtual ADX.
GSLB-Virtual ADX#debug distributed-hcheck recvd-add-list
GSLB: recvd-add-list-event debugging is on
GSLB-Virtual ADX#Recvd add list msg from peer 10.9.1.1(len = 53)
Recvd add list msg from peer 10.9.1.17(len = 53)
Syntax: debug distributed-hcheck recvd-add-list-event I sent-add-list
The recvd-add-list-event option displays messages about “health check status report received”
events. When a health check status report is received from a site ADX device, a debug message is
displayed on the GSLB Brocade Virtual ADX indicating the IP address of the ADX device as well as
the length of the health check status report.
The sent-add-list option displays messages about “health check status report sent” events. When
the site ADX device sends the health check status report to the peer GSLB ADX device, a debug
message is displayed on the site ADX device indicating the VIPs that are a part of the health check
status message. These messages help you determine if the site ADX device is sending the health
check status report at the correct interval and with the correct VIPs.
To display messages about “health check status report sent” events, enter the debug
distributed-hcheck sent-add-list command on the site ADX device. Logon to the management CLI
(through telnet, SSH or console) to see the debug log. The command undebug distributed-hcheck
recvd-add-list turns off the log.
Impact of distributed health checks on the Flashback metric
If the GSLB Brocade Virtual ADX supports the distributed health check feature, then the Flashback
metric is disabled by default. Flashback is defined as the round-trip time for a health check sent by
the GSLB Brocade Virtual ADX to the host application on the server. Flashback delay is computed
as the round-trip time of the Layer 4 health check to the TCP port and the round-trip time for the
Layer 7 health check for the application. If the GSLB Brocade Virtual ADX supports the distributed
health check feature, then the Flashback metric is disabled by default. The reason for this is that
the distributed health GSLB Brocade Virtual ADX does not carry out health checks for the host
servers load balanced by the distributed health check site ADX devices; instead the site ADX
devices periodically report this health check status information to the GSLB Brocade Virtual ADX.
Note that the distributed health check GSLB Brocade Virtual ADX still maintains health checks for
SITE-Virtual ADX#debug distributed-hcheck sent-add-list
GSLB: sent-add-list debugging is on
SITE-Virtual ADX#
Sending Address List msg: VIP = 10.9.2.16, Active = 1, Host Range = 1, Num Ports
= 2
Sending Address List msg: VIP = 10.9.2.17, Active = 0, Host Range = 1, Num Ports
= 3
Sending Address List msg: done