HP Operations Manager

Avoid unnecessary reverse name resolution


By default, HPOM performs reverse name resolution for incoming messages that contain the IP address and optionally the node name of the managed node, but no agent ID.

Such messages are typically triggered by SNMP traps and are proxied. The default reverse name resolution process calls the function gethostbyaddr() by using the IP address stored in the arriving message. Then it takes the returned node name and verifies whether it really corresponds to the name which is stored in the message.

If no node name is stored in the message, then it crosschecks whether the node name returned by the gethostbyaddr() call is known in the HPOM node configuration. If the returned node name is a short name, then it calls gethostbyname() to get the long host name (FQDN). Then it checks whether the long host name is known in the HPOM node configuration. These multiple level of checks are used to cover all kind of theoretical corner cases which might show up very rarely in well-managed environments.

The vast majority however will never hit such corner cases, so in most environments the reverse name resolution could be avoided safely if the following conditions match:

Avoiding unnecessary reverse name resolution can be configured by the value Reverse name resolution method in the Node Cache Settings namespace in the Server Configuration dialog box.

Value Possible Settings Effect
Reverse name resolution method 1 Reverse name resolution is always performed if no agent ID but IP address is contained in an incoming message. This is the default value.
  2 Reverse name resolution will be avoided if possible.

If specifying the value 2 for the registry name Reverse name resolution method then HPOM verifies the IP address differently from the default way to avoid reverse name resolution if possible, as follows: if the message contains only the IP address, but no node name, then check whether the IP address is known in the HPOM configuration. If yes, then the message can pass. If the message contains both the IP address and node name, then first check whether the pair IP address plus node name can be found in the HPOM node configuration. If yes, then the message can pass.

Otherwise HPOM performs a reverse name resolution.

Note NOTE:
If DHCP is not used and name server caching is enabled, then reverse name resolution (if required) will be fast in any case.

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