Command Line Interface Reference Guide > The SLB Configuration Menu
GSLB Metrics (Gmetrics)
Global server load balancing metric values are called gmetrics. Gmetrics are algorithms used to decide to which site a new client should be redirected. Gmetrics can load balance, maintain persistence, or be based on proximity. All GSLB metrics can be prioritized for selection order.
Available GSLB Metrics lists and describes all the gmetrics available for a GSLB rule.
Note: When a rule contains both a network metric and a remote metric, and the domain name is configured for both the rule and a virtual server, preference goes to the network metric and the servers associated with it.
For example, assume the domain name “www.a.com” is configured for a virtual server and for a rule.
If there are five configured remote real servers, but only three of them are added to the network metric, remote metric selection applies only to the three remote real servers included in the network.
 
Available GSLB Metrics 
Metric
Description
leastconns
Selects the server based on which server has the lowest session utilization. Session utilization is the percentage of sessions used over total sessions, which results in normalized sessions between servers. A server whose session utilization is 100% is considered unavailable.
If the number of possible matches is greater than the number of DNS resource records (virtual IP addresses) returned in the DNS response (as defined in the rr parameter of the rule), Alteon returns nothing and moves on to the next metric.
Requires remote site updates.
The value of this gmetric represents a percentage of the maximum connections for the relevant service, and not an absolute number.
Session utilization on one site must reach at least 1% of the maximum connections for this gmetric to operate correctly. If session utilization on both sites is equal to or less than 1%, there is no difference between the sites.
absleastconns
Selects the server (representing a global site or WAN Link) with the lowest number of currently active connections.
Note: The leastconns metric selects the server with the lowest connections utilization out of their allowed maximum.
roundrobin
Selects the server based on a round robin of servers.
Set the last metric in a rule to roundrobin or random so that the GSLB mechanism returns a value if there is at least one functional site.
response
Selects the server based on the lowest response time in milliseconds from an SLB health check of the servers.
Requires SLB health checks and remote site updates.
geographical
Selects the server based on the IANA-defined geographical region of the client source IP address.
Use the /info/slb/gslb/geo command to see a list of the IP address ranges that are mapped to each region.
The available regions are as follows:
*Africa
*Caribbean
*Pacific Rim
*Europe
*North America
network
Selects the server based on the preferred network defined for a given domain. If preferred networks are not configured, this metric is not used in the default rule.
Uses the IP address of the client’s DNS caching server, not the actual client IP address.
random
Selects the server based on uniform random distribution of the servers.
Set the last metric in a rule to roundrobin or random so that the GSLB mechanism returns a value if there is at least one functional site.
availability
Selects a server exclusively when that server is available. If that server becomes unavailable, Alteon selects the next available server. Availability is determined by a rank assigned to each server ranging from the lowest score of 1 to the highest score of 48. Multiple servers can be scored the same.
Rules that use availability as the primary metric handle failures by selecting the server with the next highest score compared to that of the server that failed, and begin forwarding requests to that server. If the server that failed becomes operational again, that server regains precedence and requests are routed to it once more.
Ensuring that the former primary server does not regain precedence is achieved by assigning the highest possible availability value (48) to the server that takes over after a failure. If this new primary server fails, its original availability value is restored and the next server in the list gains the higher precedence.
Lets you group servers based on priority, or into primary and secondary groups.
Requires SLB health checks and remote site updates.
The availability metric is applicable only when the dname in the GSLB rule is matched, provided that the virtual servers are added appropriately as the first network metric.
qos
Selects the server based on combination of the lowest session utilization and the lowest response time of the SLB health check of the servers.
Requires SLB health checks and remote site updates.
minmisses
Selects the same server based on the hash of source IP address (the IP address of the client’s DNS caching server, not the actual client IP address) and domain name. The hash calculation uses all the servers that are configured for the domain irrespective of the state of the server. When the server selected is not available, minmisses selects the next available server.
hash
Selects the same server based on the hash of source IP address (the IP address of the client’s DNS caching server, not the actual client IP address) and domain name. The hash calculation uses only the servers that are available for the domain. The server selected may be affected when a server become available or not available since the hash calculation uses only the servers that are available.
persistence
Selects the server for which the persistence cache contains the client IP address and subnet mask.
local
Selects the local virtual server only when the local virtual server is available. Applies to DNS-based GSLB only.
always
Selects the local virtual server even though the local virtual server is not available. Applies to DNS-based GSLB only.
Set the last metric in rule 1 to always so that the GSLB selection mechanism selects at least the local virtual server when all servers are unavailable.
remote
Selects the remote real servers only.
phash
Selects the server for which the persistence cache contains the client IP address and subnet mask. If the client IP address and subnet mask are not contained in the persistence cache, select the server by performing hashing on the source IP address and domain name.
bandwidth
Alteon monitors the number of octets sent between itself and real servers. Servers that process more octets are considered to have less available bandwidth. Alteon assigns requests client requests to the server with the greatest available bandwidth. When the upload and download bandwidths are configured for WAN link groups, Alteon calculates the server bandwidth based on bandwidth utilization, not on octets.
proximity
The GSLB client proximity metric measures the response time between each data center and the client. Using GSLB with the client proximity metric, Alteon selects the optimal site for the end-client, when HTTP/S redirection must be performed because local resources are unavailable. This is based on the calculated shortest response time from site to site in GSLB mode.
When configuring client proximity, carefully analyze your network mask requirements. Increasing the client IP mask reduces computation time for client proximity, because the clients with the same IP subnet mask can reuse the client proximity that is already calculated.
none
Removes a gmetric value. Alteon rule iteration passes to the next metric.