Merging Device Entries
When a new device is learned or at the time of refreshing the list contents, the module takes care to not create any duplicate entries in the list. To avoid duplicates but at the same time keep as much useful information as possible, two matching entries are merged into one which is then kept in the list.
The matching of two entries to see whether they are copies of one another is done using the device name and IP address. Two entries are considered to represent the same physical device if there is a match between EITHER the IP address or device name of one and the IP Address or name of the other. This means that there are 4 checks done and only one needs to be satisfied for there to be a match:
- Name 1 = Name 2?
- Name 1 = IP Address 2 ?
- IP Address 1 = Name 2 ?
- IP Address 1 = IP Address 2 ?
After two entries are matched, they are merged together. The result of the merge operation is an entry with attribute values derived from the two merged entries. The rules used to decide which of the two possible values to use differ for each attribute. The following table shows the attributes and how their merged value is obtained:
Attribute | Merged Value |
|---|---|
Device Name | As this is used for matching the 2 entries, it should be the same. In case of the entries has a blank name, the non-blank value is used. |
IP Address | Same rule as for the Device Name . |
Entry Status | If one of the entries is Verified , the value stored is Verified . Otherwise if one is Learned , the value is Learned . If neither of the preceding, the status of the entry with the later discovery time (more recent) is used. |
HTTP Port | The higher of the two values is kept. |
Discovery Date | The later date (more recent) of the two entries is kept. |
Response Time | The value of the entry with the later discovery time (more recent) is used. |
Router Hop Count | The value of the entry with the later discovery time (more recent) is used. |
Relay Parent Name | If one of the entries is blank, the non-blank value is used, otherwise whatever is in the database already is kept. |
Relay Enabled | If either entry has its Relay Enabled flag set, the merged entry value will also be set. |
Agent Version | The version information of the entry with the later discovery time (more recent) is used. |