Tavve zoneranger User Manual page 47

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If valid cached values are found for some but not all of the specified OIDs, a pared down
request will be forwarded to the managed device, with the OIDs associated with valid cached
results removed. When the response comes back from the managed device, the returned values
will be stored in the cache and combined with the previously located cached values and the
resulting response will be returned to the management application via the Ranger Gateway.
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If no valid cached results are found, the entire request will be forwarded to the managed device,
the returned values will be stored in the cache, and the result will be returned to the
management application via the Ranger Gateway.
Whenever an SNMP proxy request is forwarded to a managed device, the cache is refreshed based on
the results with the timestamp updated to the current time.
SNMP proxy caching is based on OIDs so that users can configure different expiry times for different
types of data. For example, information that is subject to frequent change, such as the status of an
interface (i.e. ifOperStatus) should only be cached for a short period of time, if at all, while information
that is relatively static, such as the contact name for a device (i.e. sysContact) can reasonably be cached
for a relatively long period of time.
When the ZoneRanger searches for a rule to match a requested OID value, the OID value associated
with each configured rule is treated as a prefix. As such, each rule is considered to match the specified
OID value, and also to match the tree of OID values that begin with the specified value. For example, if
the ZoneRanger were to receive a request for OID 1.3.6.1.2.1.1.4 , a configured rule with OID
value 1.3.6.1.2.1.1 would be treated as a match. This approach allows a single configured rule to
be applied to a large number of OIDs, effectively reducing the number of rules that need to be
configured. It is important to note that the configured rules are searched in order, and the first matching
rule for a given OID is used. For example, if the following rules were configured:
1.3.6.1.2.1.1.4, 10 minutes
1.3.6.1.2.1.1, 5 seconds
If a request for OID 1.3.6.1.2.1.1.4 is received, the first rule will be applied, but if a request for OID
1.3.6.1.2.1.1.5 is received, the second rule will be applied.
ZoneRanger 5.5 User's Guide 47