Smart Home Devices: The Guest Network and the Router Behind It

Additional resource for the lesson “Smart Home Devices: Guest Network and an Updated Router” — Online Security course

Speakers, doorbells, plugs, bulbs and televisions are small computers, and most of them share the Wi-Fi with your laptop and phone. This resource helps you decide which ones belong on a separate guest network, check that the router keeping them apart is still looked after, and read the one date that matters before you buy the next one.

A. Why this matters

The concern is not that a light bulb holds anything valuable. It is that, on your main network, it sits next to the devices that do. Cheaper devices are often updated less. If one of them has a flaw, that is not something you did wrong. Where the device sits decides how much the flaw matters.

A guest network keeps those devices apart from your computers and phone. But the wall between the two networks is built by the router’s own software, so the router has to stay updated too. That is why the two halves of this resource belong together.

What public guidance and the law say

The US Cybersecurity and Infrastructure Security Agency (CISA), in its guidance on securing home Wi-Fi, recommends that you “connect any smart home and other IOT devices to your Guest Wi-Fi if internet access is the only thing they require”. The UK’s National Cyber Security Centre (NCSC) adds the other half: look at how long a device will be supported before you buy it.

On the router side, the FBI’s Internet Crime Complaint Center published a warning on 7 May 2025 that routers which have reached end of life, and no longer receive updates, are being exploited in attacks. Its advice is to replace them.

The law is starting to help with the support question. In the UK, since 29 April 2024, makers of connectable products must publish a minimum period of security updates and can no longer sell them with a universal default password. In the European Union, the Cyber Resilience Act (Regulation (EU) 2024/2847) will apply its main obligations from 11 December 2027, including telling you at purchase when security support ends. Section B explains what that means for you.

B. Key concepts

Six ideas, most of which you only need to act on once.

Smart device

Anything on your Wi-Fi that is not a computer, tablet or phone: speakers, televisions, doorbells, cameras, plugs, bulbs, thermostats, printers, appliances. You may also see them called IoT devices, for “internet of things”.

Why it matters to you: Each one runs software, connects outwards, and has its own maker deciding how long it will be looked after.

Guest network

A second Wi-Fi network that most home routers can run alongside the main one, with its own name and password. CISA recommends putting smart devices on it when internet access is the only thing they need.

Why it matters to you: A device on the guest network can still reach the internet and its maker’s service, and your phone can usually still control it through the app. With guest isolation on, it should not be able to see your computers.

Guest isolation

The router setting that stops guest devices reaching the main network. It is what makes a guest network separate; some routers offer an option to relax it, with a name such as “allow guests to access my local network”.

Why it matters to you: If that option is switched on, the guest network is no longer separate. Check it once, and leave it off.

Firmware

The router’s own software. It is what creates the guest network and keeps the wall between the two networks standing.

Why it matters to you: Like any software, firmware has flaws that are found and fixed over time. A router with automatic firmware updates keeps its wall repaired without you. A router that no longer receives updates cannot, and the FBI’s advice for routers at end of life is to replace them.

The deciding question

Does this device need to reach your computers and phone directly, or only the internet?

Why it matters to you: Most smart devices only need the internet. The common exceptions are televisions and speakers you cast to from your phone, and some printers, because casting and printing need both devices on the same network.

The support date

The date until which a maker promises security updates. In the EU, the Cyber Resilience Act will require, from 11 December 2027, that the end of a product’s support period is indicated when you buy it, at least as a month and year. For products placed on the market from that date, the support period will normally have to be at least five years, unless the product is expected to be used for less, and where applicable, security updates will have to be installed automatically by default, with an opt-out. In the UK, since 29 April 2024, makers of connectable products must already publish a minimum security update period, and products can no longer ship with a universal default password.

Why it matters to you: The support date is, in practice, a “use by” date for the device’s security. A device with no date is a guess.

C. A practical example: the television that stopped casting

Priya moved everything smart in her flat onto the guest network one evening: the television, two speakers, a doorbell and three plugs. Everything still worked from her phone.

The next day she tried to send a film from her phone to the television, but her phone could not find the television. The router’s help page suggested a switch: allow guests to access the local network. It worked, and the television appeared.

Nothing Priya did was unreasonable. But that switch took the wall down for every device on the guest network, not just the television.

What changed the outcome

• Priya switched the option off again.
• She asked the deciding question about the television alone. It needs to be reached from her phone, and it still receives updates from its maker, so she moved it back to the main network.
• The speakers she only uses by voice, the doorbell and the plugs stayed on the guest network.
• She checked the router: automatic updates were on, and the provider’s page listed it as supported.

The difference was deciding one device at a time instead of opening the guest network to everything.

D. Try it yourself: sort your smart devices (25 minutes)

Four steps. Have the router’s settings page and your phone to hand. If you have never opened the router’s settings, the resource “Home Network Security: The Router Nobody Configures” shows how, and how to create the guest network.

Step 1 — List your smart devices

• Open the router’s list of connected devices, or simply walk round your home.
• Write down everything on the Wi-Fi that is not a computer, tablet or phone.

Step 2 — Sort them with the question

• For each device, ask: does it need to reach my computers and phone directly, or only the internet?
• Mark each one “guest” or “main”. Only devices you cast to, printers and anything the maker’s instructions say needs the same network go on “main”.
• For anything marked “main”, check that it still receives updates. If it does not, put it on your list to replace and, until then, consider moving it to the guest network, even if that means giving up casting or printing to it.

Step 3 — Check the router behind it

• In the router’s settings, confirm that automatic firmware updates are on.
• Confirm that the guest network does not allow access to the local network.
• Find out whether the router is still supported: on the maker’s support page for your model, or by asking your internet provider if they supplied it. If it is no longer supported, put it on your list to replace.

Step 4 — Move the first two devices

• Choose two devices marked “guest” and connect them to the guest network, usually through their app’s Wi-Fi settings or by resetting them.
• Check that they still work from your phone before moving the next ones.

Step 3 is easy to overlook, and it is the one that keeps the wall standing.

E. Videos, articles and further resources

Practical guidance first, then the laws on support periods. All in English.

Practical guidance

CISA (US) — Securing your home Wi-Fi
Router settings, including the guest network and why smart devices belong on it.
https://www.cisa.gov/audiences/high-risk-communities/projectupskill/module5

NCSC (UK) — Smart devices: using them safely in your home
What to change when a smart device arrives, and why the support period matters before you buy.
https://www.ncsc.gov.uk/guidance/smart-devices-in-the-home

FBI Internet Crime Complaint Center — End-of-life routers
The public service announcement of 7 May 2025: why routers that no longer receive updates should be replaced.
https://www.ic3.gov/PSA/2025/PSA250507

The law on support periods

GOV.UK — The UK product security regime
The security requirements that apply to connectable products sold in the UK since 29 April 2024.
https://www.gov.uk/government/publications/the-uk-product-security-and-telecommunications-infrastructure-product-security-regime

EUR-Lex — Regulation (EU) 2024/2847 (Cyber Resilience Act)
The official text of the EU regulation: support periods, security updates and when each part applies.
https://eur-lex.europa.eu/eli/reg/2024/2847/oj/eng

Links checked in October 2026. If an address changes, searching for the title on the organisation’s site usually finds it. Router menus name these settings differently; the support pages of your router’s maker or your internet provider document your model.

F. The Cyber Welfare Framework: Skills, Awareness, Secure Behavior

This lesson sits on the Skills pillar at level FL2: a setting made once, which then keeps working without you.

Skills

• Deciding, device by device, whether it belongs on the guest network.
• Checking guest isolation and automatic firmware updates in the router.
• Finding out whether a router or device is still supported.

Awareness

• Understanding that the separation is built by the router’s software, and is only as good as its updates.
• Knowing that casting and printing need devices on the same network, and handling that as an exception.

Secure Behavior

• Giving every new smart device the guest network unless it has to reach your computers.
• Looking for the support date before buying a connected product.

G. Questions to sit with

• Which smart device in your home would you move to the guest network first?
• When did your router last receive an update, and who would tell you if it stopped?
• For the last smart device you bought, do you know until when it will receive security updates?

H. What to do now

The recommendations (R) and security measures (MS) from the Cyber Welfare database closest to this topic. A guest network for smart devices is not yet a recommendation of its own, but it is one of the most useful steps in this resource.

1. Separate

• R1 — A unique password for the guest network, for each device’s app account, and in place of any default password.
• R2 — Keep those passwords in a password manager, so a different one for each costs you nothing.

Minimum commitment: move two devices that only need the internet onto the guest network today.

2. Keep the wall repaired

• R6 — Keep software up to date, including the router’s firmware and every smart device, with automatic updates on.
• R20 — Wipe a smart device before you pass it on or dispose of it, so your Wi-Fi password and account details do not go with it.

Minimum commitment: confirm that your router’s automatic updates are on, and find out whether it is still supported.

In short

• Most smart devices only need the internet. Put those on the guest network, as CISA recommends.
• The wall between the two networks is built by the router’s software. Keep it updated, and replace a router that is no longer supported.
• For devices you cast to or print from, decide one at a time. Do not open the guest network to the main one.
• Before you buy, look for the support date: in the UK makers must already publish one, and in the EU it will have to be shown at purchase from December 2027.

Related resources in this course

• Home Network Security: The Router Nobody Configures
• Home Network Attack Surface: Counting What Is Connected
• Device Updates: What Happens When They Stop Arriving

Discover more companion resources from the online courses of the Protect Your Digital Privacy programme.