Alteon Application Switch Operating System Application Guide
Health Checking
488
Document
ID:
RDWR-ALOS-V2900_AG1302
TCP and UDP-based DNS Health Checks
Alteon supports both TCP and UDP-based DNS health checking. This health check is performed by
sending a DNS query over either protocol and monitoring the server reply.
The following DNS-specific arguments are available:
•
Protocol—Specifies whether the DNS health checks should be performed using UDP (default) or
TCP protocol.
•
Domain—Specifies the domain name that must be resolved (up to 63 characters). An Inherit
value can be configured to allow definition of the domain using the group content parameter. If
no domain name is configured, the health check is performed by sending a query for a dummy
host and watching for the server's reply. The reply, even though it is negative (for example, the
reply is “Server not found” since the query is for a dummy host), serves the purpose of a health
check.
Pre-defined udpdns (DNS over UDP) and dns (UDP over TCP) health checks are available for simple
DNS service monitoring. The domain parameter of the pre-defined health checks is set to Inherit,
allowing definition using the group content and the destination port set to standard DNS port (53).
TFTP Health Check
Alteon supports the Trivial File Transfer Protocol (TFTP) health check, which uses the TFTP protocol
to request a file from the server. At regular intervals, Alteon transmits TFTP read requests (RRQ) to
all the servers in the group. The health check is successful if the server successfully responds to the
RRQ. The health check fails if Alteon receives an error packet from the real server.
The following TFTP-specific argument is available:
•
Path/Filename—Specifies the file name requested (up to 256 characters). Depending on the
implementation of the TFTP daemon on the real servers being health-checked, you may have to
specify the full pathname of the file (/tftpboot/<filename>) on some systems. On others, a
filename is sufficient. By default, if no path is specified, the switch checks the /tftpboot folder.
An Inherit value can be configured to allow the file configuration using the group content.
Note:
If no filename is specified (directly or via group configuration), the health check performed
for that group is TCP.
A pre-defined tftp health check is available for simple TFTP service monitoring. The health check has
the path or filename parameter set to Inherit, allowing definition using the group content and the
destination port set to standard TFTP port (69).
SNMP Health Check
Alteon supports SNMP health checks by sending an SNMP GET request to the real server running an
SNMP-based agent. SNMP health checks can be used on any real servers, provided they have an
SNMP agent. The SNMP health check is performed by polling a single variable within the MIB.
The health check is successful if a valid response is received and the returned value is within a
configured range or if it matches a configured string.
The SNMP health check response can also be used to dynamically readjust monitored real server
weights.
The following SNMP-specific arguments are available:
•
OID—Specifies the OID whose value the health check attempts to retrieve.
•
Community—Specifies the community name that the system must use to authenticate with the
host server through SNMP.
