A About the absRelativePosition Value
This appendix explains how to generate the absRelativePosition variable value.
Generating the absRelativePosition Value
The field contains a variable called absRelativePosition which is used to generate a unique value for an entity in a given tree. absRelativePosition is a programmatically generated value and is composed of a prefix and suffix. The suffix is always derived from entPhysicalParentRelPos.
The following is an example of a physical device tree: PD E1 PP1 E2 PP2
The prefix of each entity is derived from the absolute relative position from the root; for example:
PD takes the prefix 0
The child E1 takes the prefix 0:0
The child E2 takes the prefix 0:1, uniquely identifying itself from its sibling.
PP1 takes the prefix 0:0:0
PP2 takes the prefix 0:1:0
Some devices (due to a device reporting error) show that multiple equipment holders or physical ports have entPhysicalParentRelPos value that occupy the same relative position under their parent.
At a high level, the algorithm works by resolving conflicts by increasing the relative position of the subsequent duplicates by 1. This is best described using an example.
Table A-1 shows the applicable SNMP attributes that are used in determining the correct relative position.
Table A-1 SNMP Attributes Used to Determine Correct Relative Position
| Index | entPhysicalDesr | entPhysicalParentRelPos | entPhysicalContainedIn |
|---|---|---|---|
|
1 |
3640 chassis, Hw Serial#: 621974280, Hw Revision: 00 |
-1 |
0 |
|
2 |
3640 Chassis Slot |
0 |
1 |
|
3 |
Ethernet/WAN |
0 |
2 |
|
12 |
AmdP2 |
0 |
3 |
|
13 |
AmdP2 |
0 |
3 |
|
14 |
AmdP2 |
1 |
3 |
|
15 |
AmdP2 |
1 |
3 |
Where the headings in Table A-1 have the following significance:
-
Index: A numeric value used to represent a physical entity and must be unique.
-
entPhysicalDesr: A string description of the physical entity.
-
entPhysicalParentRelPos: The relative position within the context of its parent.
-
entPhysicalContainedIn: The Index of the parent entity denoting the current entity as a child. 0 indicates the root of the physical entity tree.
From Table A-1, notice that AmdP2 at index 12 and 13, and AmdP2 at index 14 and 15 have the same entPhysicalParentRelPos values (that is, 0 and 1 respectively) within the context of its parent, which is Ethernet/WAN.
-
Index 12 and 13 would both generate the name AmdP2::0.
-
Index 14 and 15 would both generate the name AmdP2::1.
To correct this, the algorithm briefly described above is executed as follows:
-
Index 12 is processed first and would generate the name "AmdP2::0".
-
Index 13 is processed and it is determined that the entPhysicalParentRelPos is a duplicate. The cartridge increments the value by 1 and generates the name "AmdP2::1". It also flags this entity's position as artificially generated.
-
Index 14 is processed and it is determined that an entity already exists with entPhysicalParentRelPos 1, however it was artificially generated. Therefore, Index 14 gets the name "AmdP2::1" and Index 13 gets the name "AmdP2::2".
-
Index 15 is processed and it is determine that the entPhysicalParentRelPos is a duplicate. The cartridge increments the last artificially generated value by 1 thereby creating name "AmdP2::3".
Table A-2 shows the result.
Table A-2 End Result
Index entPhysicalDesr Name 12
AmdP2
AmdP2::0
13
AmdP2
AmdP2::2
14
AmdP2
AmdP2::1
15
AmdP2
AmdP2::3