# Front, rear, and rack units disagree > Describe the complete equipment footprint so front and rear records point to the same device. Canonical page: https://datacenterlabeling.com/problems/rack-face-and-u-position Source review: 2026-09-12. This is a source-review date, not a claim of standards certification. Rackstamp provides editorial field guidance. IDs, cases, and worksheet entries are fictional examples unless identified otherwise. Distinguish local conventions from adopted standards. Source notes describe the evidence scope; a linked overview is not the full standard or a project approval. ## The practical answer Record rack position as a complete equipment footprint: rack, mounting face, occupied units, and the rule used for the stored position. Compare both physical faces with the same asset record. A difference between a printed rack number and a database position may reflect different conventions; resolve that translation before moving a label or changing the recorded location. ## When to use Use this guide when an elevation, work order, and physical rack disagree about face or U position. Resolve the reference before selecting equipment from the record. NetBox records rack face and base position separately. For multi-U devices, it uses the lowest-numbered occupied rack unit. This is NetBox's convention, not a rule to impose on every drawing or manufacturer instruction. [NetBox device model](https://netbox.readthedocs.io/en/stable/models/dcim/device/) ## What to gather Collect the rack elevation, device asset ID, occupied-unit information, the site's numbering direction and position rule, and permitted front/rear observations. ## Method 1. Confirm the rack and device identity before interpreting a U value. Record an asset identifier that distinguishes the device from similar equipment above or below it. 2. Write down the numbering direction and the reference used by each record. Distinguish lowest-numbered unit, top mounting point, and other documented references. 3. Record the full occupied range and height. For equipment without a numbered U position, describe the actual mounting location rather than forcing a fictional rack-unit value. 4. Compare front and rear views using the device identity and footprint. State the mounting face separately from the face from which a label is being read. 5. Resolve any conversion between the elevation's convention and the inventory's convention. Keep that rule with the record and have another person check both views before closing the discrepancy. ## Separate a reference mismatch from an actual location error Begin with the identity of the rack and equipment. A drawing can show the correct U value for a different cabinet, and two similar devices can occupy adjacent positions. Confirm the complete rack address and a distinguishing asset reference before interpreting the elevation. If either identity is uncertain, resolve that uncertainty first; arithmetic cannot repair a mismatched object. Next ask whether the compared records use the same meaning for position. One may record the lowest-numbered occupied unit, another the top of the illustrated footprint, and a third a mounting reference defined by its own system. The numbers can differ while describing the same physical span. Record each meaning in words before changing either value. If the meanings agree but the occupied ranges differ, treat the issue as a possible stale or incorrect record. Compare the permitted observation with the relevant installation or move history. If the range agrees but the face differs, separate the mounting face from the face used to view or service the equipment. A rear photograph can show a front-mounted device's connectors. When the rack's numbering direction or rail reference is unclear, record that missing definition. Do not assume that a familiar elevation template describes the installed rack. The task is to reconcile actual references, not make the display look conventional. ## Build an observation that describes the complete footprint Record the lowest and highest numbered units actually represented by the equipment footprint, using the site's approved observation process. Preserve leading zeros or U prefixes where the relevant record requires them. Record height separately so the reviewer can compare the span and the entered height rather than relying on one unexplained number. Describe which physical unit markings and equipment identity support the observation. A photograph or sketch should show enough context to distinguish the intended asset from the item above or below it, where permitted. If a door, cable manager, or access restriction hides part of the reference, state what could and could not be confirmed. Do not fill the hidden part from memory and call the span observed. Keep separately managed mounting or service components explicit in the supporting record. A nearby shelf, panel, or accessory may have its own identity and footprint under local policy. The equipment manufacturer's documentation and the site's asset model determine how those components are represented; this worksheet should not merge them merely because they appear together in a view. For equipment mounted outside the numbered rack-unit footprint, record its actual mounting location and the system's supported representation. A side-mounted item should not receive an invented U position just to satisfy a spreadsheet cell. Escalate a mandatory-field limitation to the records owner and retain the descriptive evidence. ## Translate between systems without rewriting the observation Create a comparison for each system that stores the location: system name, current value, documented position meaning, and proposed corrected value. Keep the observed occupied range as the common reference. This makes it possible to see whether the change is a translation, a stale location, or a data-entry correction. For example, a fictional three-unit span from U31 through U33 has a lowest-numbered-unit reference of U31 and an upper-unit reference of U33. Those values describe the same span only when the systems explicitly use those respective meanings. The example is a translation exercise, not an instruction to configure a particular product. State how the translation handles height and direction. A conversion that happens to work for a one-unit asset may fail for taller equipment or a differently numbered rack. Test the rule against the actual examples in scope, including a multi-unit device and any case where the source drawing's orientation differs. Have the system owner confirm the meaning of its fields rather than inferring it from the screen layout. Record the translation rule beside the correction evidence or link a controlled mapping document. A number changed without its explanation can be “corrected” back by the next import. Ask the owner of the originating drawing, inventory feed, or template to align that input with the documented rule. ## Treat mounting face and viewing face as different facts Define mounting face using the record system and installation documentation applicable to the equipment. Define viewing face as the side from which the supporting observation was made. The worksheet's mounting-face field should not be populated merely by copying a photo filename containing the word “rear.” When the same equipment is visible from both aisles, reconcile both views through its physical identity and occupied span. Do not create a second asset record simply because the rear connectors appear in a different photograph. Conversely, a rear-mounted panel visible near a server is not necessarily part of that server. Confirm separate identities and the actual arrangement. Where records describe front and rear occupancy differently, involve the elevation owner before applying a blanket rule. Keep the particular collision or discrepancy visible: which assets, which spans, and which face semantics disagree. The source data may require a correction to the device type, location, or representation rather than only a face label. Use a drawing legend or written note that tells readers how the two views relate. A mirrored visual layout should still preserve each asset's identity. The person reviewing the rear should be able to understand the view without mentally reversing unexplained coordinates. ## Scenario: a move closeout copied the top visible unit In a separate fictional case, AST-G04-301 occupies U31–U33 in DC01/H1/R301 and is front-mounted under the local record convention. The inventory expects the lowest-numbered occupied unit, but the move closeout entered U33 after reading the top visible rail marking. A rear service photograph was also used to populate the face as Rear. The reviewer opens POS-G04-301 and confirms the asset identity, full occupied span, and the inventory's documented field meanings. The installation evidence supports U31–U33 and Front mounting. The diagnosis is two reference errors in the closeout record, not an instruction to move the equipment. The proposed correction changes record position to U31 and mounting face to Front. It retains the observed height of 3U and records Rear as the viewing side of the supporting service photograph. The move record and elevation are updated through their owners so a later import will not restore U33 and Rear. An independent reviewer uses the corrected elevation to identify AST-G04-301 from the permitted front and rear views. They confirm that the same physical asset spans the same three units in both references. Closure retains the original values, their cause, the corrected fields, and the supporting evidence. If a portion of the footprint had remained inaccessible, that part of the verification would remain unresolved rather than being covered by the successful field translation. ## Reconcile established racks and new-build elevations In an established data hall, begin with a bounded discrepancy and its most recent change history. Rack elevations often combine records created at different times. Identify which entries follow which documented convention before converting an entire rack. A successful correction to one asset does not prove that every neighboring entry has the same cause. Look for reused locations and retired equipment when the current span appears to overlap an old record. Establish whether the old entry remains active erroneously or represents valid history. Keep the former occupant linked to its removal or move event. Do not resolve an apparent overlap by shrinking the current asset's footprint to make the drawing fit. For a new build, review the elevation convention before the equipment schedule becomes the source for labels and inventory imports. Include a multi-unit example and examples viewed from both faces. Ask the receiving team to locate the same assets using the drawing and the proposed inventory representation. This reveals semantic mismatches while the mapping rule can still be corrected in a bounded set of records. When a rack or model changes, compare the new arrangement with the released elevation rather than assuming the old template remains appropriate. Keep the physical installation authority separate from the record correction: this guide describes reconciliation evidence and does not authorize remounting hardware. ## Resolve recurring failures at their source If every multi-unit asset is displaced by the same apparent amount, inspect the meaning of the source position field before correcting rows individually. A systematic top-versus-bottom mismatch can be a mapping problem. Document the actual affected rule and examples, then have the data owner review the transformation that produced the records. If only one row is wrong, compare its work package, observed span, and editing history. The cause may be a transposed digit, stale move record, or wrong asset selection. A narrow correction is easier to review when the record states which of those causes was established. If an operator reads the correct label but repeatedly selects the wrong item, review whether the label or work order carries enough context. Rack address, asset identity, footprint, and face each answer different questions. Do not overload a single U number with all of them. ## Record a closeout another shift can follow The final evidence should show the observed footprint, the position rule, the corrected system values, and the identity connecting both rack views. Record who approved a semantic translation and who checked the physical references. A reviewer should be able to distinguish a verified location from a value translated under a documented rule. List any dependent elevations, work orders, or imports that still need correction. Keep pending system work visible even if the physical observation is complete. Once the affected records agree under their declared meanings, retain the conversion explanation with the discrepancy so the next shift does not reopen the same disagreement. ## Worked example Fictional rack DC01/H1/R014 uses ascending numbering and a lowest-numbered-unit record position. ```text Rack DC01/H1/R014 FRONT VIEW REAR VIEW U25 [other asset] [other asset] U24 [AST-008421] [AST-008421] U23 [AST-008421] [AST-008421] U22 [empty] [empty] Record position U23; occupied range U23-U24; height 2U ``` The rear view retains position U23 for the same asset. This fictional diagram supplies location information only. ## Common mistakes - Recording only the top visible U number without stating the convention. - Treating a rear-view label as proof of rear mounting. - Assigning a U number to equipment mounted outside the numbered footprint. ## Verification - [ ] Rack and asset identities match both views. - [ ] Occupied range agrees with recorded height. - [ ] Position rule is written explicitly. - [ ] Mounting face and viewing face remain distinct. - [ ] Any convention conversion has been independently checked. ## Worksheet: Rack elevation and label-placement worksheet Fields define one row; sample values are fictional. Leave working-sheet dates blank until their recorded event occurs. Sample status: **Example only**. | Field | Definition | Filled example | | --- | --- | --- | | Rack | Approved rack identifier. | DC01/H1/R014 | | Asset ID | Identity of the equipment being located. | AST-008421 | | Mounting face | Primary face used in the installation record. | Front | | Occupied units | Full numbered equipment footprint. | U23-U24 | | Height in U | Number of occupied rack units. | 2 | | Position rule | Reference used to select one position value. | Lowest-numbered occupied U | | Record position | Value entered under that rule. | U23 | | Owner | Role responsible for the elevation. | Rack documentation lead | | Evidence | Elevation and observation references. | DEMO-ELEV-R014 rev 2 | | Verifier | Person checking both face references. | Example reviewer | | Verification date | Date the comparison was completed. | 2026-09-12 | | Status | Review state. | Example only | ## Frequently asked questions ### Which convention wins when two systems differ? Use each system's documented semantics and record the translation. Escalate a missing rule to the record owner instead of silently changing the value. ### Can a rack label identify equipment by U alone? Include enough context to distinguish the rack, equipment, and footprint. A U value alone cannot resolve two different rack identities. ### Is a rear-view photograph enough to set the mounting face? No. Record Rear as the viewing side of that evidence, then establish mounting face from the applicable installation record and system semantics. The two facts may differ for the same device. ### What if the equipment spans units that cannot all be seen? Record the visible portion and the limitation. Obtain the missing evidence through an approved observation or authoritative installation record, and distinguish observed from documented information. Do not guess the hidden boundary to complete the height field. ### Should an apparent overlap be fixed by changing the U number? First establish the identities, faces, footprints, and event histories involved. The apparent conflict may be a retired record, a reference mismatch, or an actual discrepancy. Changing a value merely to remove the overlap hides the cause. ## More worked label examples ### Translate a three-unit footprint into one record position The example uses a stated lowest-occupied-U rule and records both the occupied span and mounting face. ```text SCOPE: DC01 / H1 / R101 LOCAL RULE: bottom-up U numbering; record lowest occupied U FRONT ELEVATION RECORD U24 [ empty ] U23 +--------------------+ Asset: AST-G04-101 U22 | AST-G04-101 | Mounting face: Front U21 +--------------------+ Occupied: U21-U23 U20 [ empty ] Height: 3U; position: 21 LABEL FACE +----------------------------+ | AST-G04-101 | | DC01-H1-R101 FRONT U21-U23 | +----------------------------+ Before record: U23 / 3U -> After record: U21 / 3U Correction reference: POS-G04-101; span observed U21-U23 ``` - Substitute the position semantics used by your inventory system. If it records the top occupied unit, the numeric position changes while the observed U21-U23 footprint remains the same. - Read the rack rail numbering and check the complete equipment height, including any separately managed mounting components. Do not derive the footprint from a nameplate height alone. ### Separate mounting face from rear service access A server reached from the rear remains front-mounted in this fictional rack record; a rear-mounted panel is a different object. ```text SCOPE: DC01 / H1 / R201 OBJECT LABEL FACES +---------------------------+ +---------------------------+ | AST-G04-201 | | PNL-G04-201 | | FRONT MOUNT / U12-U13 | | REAR MOUNT / U36 | +---------------------------+ +---------------------------+ OBJECT MOUNTING FACE OCCUPIED U SERVICE VIEW AST-G04-201 Front U12-U13 Rear connectors PNL-G04-201 Rear U36 Rear ports REAR PHOTO EV-G04-201 -> asset AST-G04-201, connector view REAR PHOTO EV-G04-202 -> panel PNL-G04-201, mounting view Position rule: lowest occupied U; server=12, panel=36 ``` - Use distinct fields for mounting face and the face from which a connection is serviced. A photograph of rear connectors does not establish rear mounting. - If equipment has components on both faces, record their actual arrangement and any separate asset identities. Check the full elevation for collisions before accepting a position correction. ## Sources and applicability - [NetBox: Device model](https://netbox.readthedocs.io/en/stable/models/dcim/device/): Product-specific face and position semantics; local elevation translation is editorial guidance. The expanded triage, decision comparisons, scenarios, and closeout procedures are original editorial guidance. ## Related guidance - https://datacenterlabeling.com/problems/rack-wayfinding - https://datacenterlabeling.com/problems/asset-versus-location - https://datacenterlabeling.com/problems/patch-panel-port-mapping