# What a Network Refresh Actually Involves > What a network refresh project actually involves: the survey that comes first, the PoE power budget, uplink decisions, lead times and how a cutover runs. *Source: https://trybussolutions.com/what-a-network-refresh-involves/ · Trybus Solutions · Chattanooga, TN · 423-633-1817 · info@trybussolutions.com* - [Home](https://trybussolutions.com/) - Company[About us](https://trybussolutions.com/about-us/) - [Careers](https://trybussolutions.com/careers/) - Solutions[Collaboration](https://trybussolutions.com/collaboration-unified-communications/) - [Networking & Connectivity Solutions](https://trybussolutions.com/networking-connectivity/) - [Cybersecurity Solutions](https://trybussolutions.com/cybersecurity/) - [Cloud & Infrastructure](https://trybussolutions.com/cloud-and-infrastructure/) - [Governance, Risk & Compliance](https://trybussolutions.com/governance-risk-compliance/) - [Digital Workplace](https://trybussolutions.com/digital-workplace/) - 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What a Network Refresh Actually Involves # What a Network Refresh Actually Involves July 16, 20269 min readNetworking ## Why a Refresh Starts Very few organizations replace switching because they want newer switching. The refreshes we are brought into begin for one of four reasons, and which one it is shapes the budget more than the equipment does. End of support is the most common, and it is a sequence of dates spread over years. Cisco publishes its policy in full and the shape is typical: an end-of-life announcement, end of sale about six months later, and a last date of support five years after that for hardware. Software support ends earlier than hardware support, and critical bug and vulnerability fixes stop earlier still. That earlier date is usually what moves a budget. - **End of support** The equipment still works. Software fixes stop, spare parts get harder to source, and a cybersecurity assessment has a finding to write up. - **A power budget that ran out** Cameras, door controllers, access points and phones all landed after the switches were bought. The closet ran out of watts before it ran out of ports. - **An acquisition** Two address plans, two naming conventions, two ideas about VLAN numbering, and a deadline set in finance. - **A building change** A fit-out, a consolidation or a lease ending. Construction then drives the network schedule, and those schedules move. ## The Survey That Has to Happen First A design written from a spreadsheet of port counts is a guess. The first stage is walking the building and opening every closet, which always takes longer than expected. The cable plant constrains the design more than anything else and gets checked least. If the refresh is meant to bring 10 Gigabit to the desk, the category and condition of the horizontal cabling decide whether that is possible without pulling new cable. Category 6A supports 10GBASE-T over the full 100 meter channel. Over generic Category 6 the reach is shorter and depends on alien crosstalk from surrounding bundles, which is why the IEEE task force behind 10GBASE-T set its objective at least 55 meters to 100 meters over Category 6 or better. Certification testing settles it. Trybus does not pull cable. On the networking and connectivity work we run, we survey the building, write the specification and coordinate the cabling partners who install against it. - **Closet space** Rack units free, and whether new and old switching fit side by side. - **Power and cooling** Circuits, receptacle types, UPS runtime, and whether a closet fine with two switches stays cool at a higher draw. - **Riser and pathway capacity** Room left in sleeves and trays for more fiber, and whether the pathway survived other trades. ## The Power Budget Is the Number That Surprises People Every powered device draws from a finite budget in the switch, and that budget is a property of the power supplies installed rather than the port count. The standards set the ceiling per port: IEEE 802.3af allows up to 15.4 W per port, 802.3at raises that to 30 W, and 802.3bt uses all four pairs to go further, with Type 3 reaching 60 W and Type 4 supplying between 45 W and 90 W at the switch for a device drawing between 40 W and 71.3 W. The arithmetic is straightforward and almost always skipped. Count the access points, the cameras, including any with pan-tilt-zoom motors or heaters that draw far more than a fixed dome, the door controllers, the phones and whatever facilities has connected, then compare the total against what the supplies deliver with one of them out. What happens when the budget is short is worth knowing in advance. On Cisco Catalyst switching, when there is not enough power, the switch denies power to ports in auto mode in descending order of port number, then to static-mode ports the same way. Nothing in that decision knows which port has the badge reader on it. Anything that must stay up needs a static allocation and a documented port. Heat is the other half. Power in a cable becomes heat in a bundle, and the National Electrical Code derates what a four-pair cable can carry as bundle size grows, in Article 725.144. TIA’s TSB-184-A covers the same ground from the cabling side, in temperature rise rather than amperage. In practice the useful thing to put in a specification is a cap on bundle size, because an installer can be inspected against a cable count where a derating table has to be recalculated on site. ## Stacking, Redundancy and Uplinks The design decisions in a closet refresh are few, and most are about what happens when something fails. On larger estates they get settled in architecture and solution design before anything is quoted, because they move the bill of materials. Stacking is the first. A stack gives one management point, one configuration and ports that behave as though they came from one switch, which is why most access closets end up stacked. The cost is shared fate: one software version across the members, and upgrades that need planning if the closet cannot go dark at once. Independent switches avoid that and leave more configuration to keep aligned. Uplinks are where the survey pays for itself. The fiber strands in the riser decide how much uplink you can build, and whether a closet can reach two distribution points by separate paths. Plenty of buildings have exactly two strands to a closet, which forecloses the dual-homed design somebody drew in a meeting. - **Stack or standalone** One management point and shared fate, against separate boxes with independent upgrades and more configuration. - **Uplink capacity** Sized for what the closet carries in five years, limited by the strands in the riser. - **Power redundancy** A second supply is only redundant if the remaining one carries the full PoE load. Sizing the spare into the budget loses it. ## Lead Times Set the Schedule, Not the Engineering Ask how long a refresh takes and the honest answer is that the engineering is rarely the constraint. Hardware availability, optics, licensing paperwork and cabling materials set the dates, and each has its own queue. Optics often arrive on a different schedule from the switches they belong in, a small detail that stops a build completely. Nothing can be ordered until the design is locked, so every week of indecision adds a week at the far end. If an end-of-support date is driving the refresh, count backward from it and include the ordering window, the staging time and the change windows you can realistically get. The gap between that arithmetic and the date in the budget request is the real risk. Staging is what makes cutover nights short. Equipment configured, labeled and tested on a bench before it travels leaves only racking, patching and verification in the closet. ## How the Cutover Actually Runs Refreshes run closet by closet, or site by site, inside agreed change windows. On a larger project one closet goes first and everyone learns from it, and the second window is always shorter than the first. On a single-closet job that pilot stage often is not worth the time, and we will say so. Each site is followed by a period of closer support while the snags come out. Every window needs a defined way back before it starts. In practice the old switch stays racked and powered until the new one is accepted, the patching is photographed before anything is unplugged, configurations are backed up off-box, and there is a stated time at which the team stops troubleshooting and reverts. Somebody owns that call. The acceptance test list turns a cutover into a sign-off, and it should be written during design, when nobody is tired. Verify that every powered device came back up, check a call over the wireless, walk a badge reader and a printer, and confirm anything tied to building systems, alarms or paging still reports. Those devices fail silently and get discovered days later by a user. - **Before the window** Port map and patch photographs, configurations backed up off-box, staged equipment on site, and contacts for the building and the monitoring provider. - **The rollback trigger** A stated time and a named owner. If the criteria are not met by that clock, the change reverts and the window is rebooked. ## What You Should Be Holding at the End A refresh that leaves you with working equipment and no documentation has moved the problem forward a few years. This is what we produce on a typical mid-size refresh, and which of it you need is agreed at scoping. The build sits under implementation and migration, and whether your team runs the result afterwards or hands it to managed services and support is a separate agreement. - **As-built diagrams** Physical and logical, matching what is installed on handover day. - **Addressing, VLAN and port allocation** The plan as built, the labeling scheme written down, and which ports carry static PoE allocations. - **Configuration backups and software versions** Held where your team can reach them without calling anyone. - **A power budget per closet** What draws power today, what the supplies deliver with one out, and the headroom left. - **Cabling certification results** Handed back by the cabling partner when the links are in. - **Serials, entitlements and support dates** What is covered and until when, which is also when the next refresh conversation starts. ## Common questions ### How long does a network refresh take? It depends far more on hardware lead times, optics availability and how many out-of-hours change windows you can get than on the design work. A single-site access refresh can be a matter of weeks once equipment is on site. A multi-site estate is a program measured in months. Anyone giving you a duration before discovery has finished is guessing. ### Do we have to replace equipment just because it is going end of support? Not automatically. The equipment keeps working, and plenty of it has years of service left. What changes is that software and vulnerability fixes stop before the last date of support, spare parts get harder to source, and any risk assessment done after that point carries a finding. The question is how much risk the business will hold and for how long, and it is worth deciding deliberately. ### Can we reuse the cabling we already have? Often, for gigabit to the desk. It becomes a real question if the refresh is meant to deliver 10 Gigabit over copper, where category, length and the alien crosstalk environment all matter, or if PoE loads are rising enough that bundle heat becomes a factor. Certification testing on a sample of links answers it quickly and costs far less than finding out after the switches are installed. ### Do you install the cable? We do not pull cable ourselves. We survey the building, write the specification and coordinate the cabling partners who install against it, then check the results before the switching goes on top. ### Do we need a wireless survey if we are only replacing switches? If the access points and their placement are unchanged, usually not. If access points are being replaced, moved or added, or if the power available to them changes, then the coverage and capacity assumptions have changed with them and a validation survey is worth the time. ## Sources - [Cisco - End-of-Sale and End-of-Life Products Policy](https://www.cisco.com/c/en/us/products/eos-eol-policy.html) - [Cisco - Configuring Power over Ethernet, Catalyst 9300 interface and hardware configuration guide](https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9300/software/release/17-12/configuration_guide/int_hw/b_1712_int_and_hw_9300_cg/configuring_poe.html) - [IEEE Std 802.3bt-2018 - Physical Layer and Management Parameters for Power over Ethernet over 4 Pairs](https://standards.ieee.org/ieee/802.3bt/6749/) - ANSI/TIA-TSB-184-A - Guidelines for Supporting Power Delivery over Balanced Twisted-Pair Cabling - [CommScope - Cat 6A: The Fact File](https://www.commscope.com/insights/the-enterprise-source/cat6a-the-fact-file/) ## Keep reading - [WirelessWireless Site Surveys and What Predictive Design Misses10 min read](https://trybussolutions.com/wireless-site-survey-predictive-design/) - [SecurityNetwork Segmentation Without Stopping the Business10 min read](https://trybussolutions.com/network-segmentation-without-stopping-the-business/) - [Contact CenterContact Center Migration: What to Scope First9 min read](https://trybussolutions.com/what-to-scope-before-choosing-a-contact-center/) ## Get the survey done before the budget is set Trybus Solutions establishes what the closets, the power and the cable plant can actually carry, then designs and delivers the refresh around it. 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