#ASUS #ZenWiFi #BD4 #Review #LowCost #Effective #WiFi #System
The ZenWiFi BD4 was first available at the end of 2024. I’ve used one since the beginning of 2025 and intended to review it first. However, I ended up testing the slightly higher-end ZenWiFi BD5 due to the availability of its outdoor option, among other things, and realized the two are mostly identical.
This quick review aims to demonstrate that the ZenWiFi BD4 is very similar to the ZenWiFi BD5 in real-world usage, with the latest firmware, despite their one major difference in hardware specs. It’ll help you decide which one to pick. The two are so similar that I decided not to test the ZenWiFi BD4 for official performance scores. You can use those of the ZenWiFi BD5 as a reference.
Here’s the bottom line: If you have a wired home, the ZenWiFi BD4 is a better deal than its stronger cousin thanks to the lower cost. For those with Gigabit or lower broadband, the two are practically the same in real-world experience, no matter how you use them. However, if you want to get a bit more than Gigabit, the ZenWiFi BD5 has a slight edge in a fully wireless setup.
If you have higher bandwidth needs, pick a tri-band Wi-Fi 7 ZenWiFi alternative instead.
Dong’s note: I first published this piece on December 4, 2024, as a preview and updated it to a review on September 7, 2025, after extended real-world usage.
ASUS ZenWiFi BD4: The bare-minimum Wi-Fi 7 ZenWiFi
If the ZenWiFi BD5 is the rival of the TP-Link Deco BE25, the ZenWiFi BD4 is the answer to the Deco BE23 (a.k.a Deco BE3600). It represents ASUS’s bare minimum in Wi-Fi 7 hardware, with a total theoretical bandwidth of 3600Mbps. To put things in perspective, many Wi-Fi 6 or Wi-Fi 6E sets, such as the ZenWiFi XT8 and ET8, for example, each have 6600Mbps of total Wi-Fi bandwidth.
The low bandwidth results from the fact that the BD4 has only two bands—5GHz and 2.4GHz—instead of three, unlike the BT8 or BT10. Additionally, its Wi-Fi hardware also has entry-level specs. Specifically, its 5GHz band doesn’t feature 240MHz channel width, which the ZenWiFi BD5 does—this is the only difference between the two.
Since late 2024, the dual-band approach has become familiar in Wi-Fi 7 broadcasters. There have been numerous dual-band routers and Wi-Fi systems from different vendors. They are a testament to the fact that the 6GHz band is complicated. The cabinet below includes some details about how this band is being adopted around the world.
How the 6GHz band is regulated around the world
The 6GHz band has a total width of 1200 MHz, ranging from 5.925 MHz to 7.125 MHz, and is divided into 59 channels of 20 MHz each. These channels are grouped to create “sub-bands,” which also vary from one region to another.
In the U.S., the FCC has designated four sub-bands across the entire 6GHz spectrum, including UNII-5, UNII-6, UNII-7, and UNII-8, for Wi-Fi use, though portions of the band may be reserved for other applications.
The E.U. Commission allows only the UNII-5 equivalent part of the frequency for Wi-Fi use, which is 480 MHz in width from 5925 MHz to 6425 MHz. Some other parts of the world are somewhere in between, with the UNII-5 portion adopted and the rest being considered. In the rest, this band may not even be available for Wi-Fi at all.
Generally, Wi-Fi 6E needs a 160MHz channel to deliver the best performance, and Wi-Fi 7 requires double that, 320MHz. Due to spectrum availability and other reasons, real-world hardware tends to use narrower channels in most cases.
Overall, the use of the 6GHz frequency is complicated and is the main reason a Wi-Fi broadcaster made for one region might not work in another.
The table below shows its current adoption worldwide. The “Considering” portion is generally slated to be finalized eventually, though that varies from one region to another.
| Country | Adopted Spectrum |
|---|---|
| United States | 5925-7125 MHz (entire band including UNII5, UNII-6, UNII-7, and UNII-8) |
| Albania | 5945-6425 MHz (UNII-5) |
| Andorra | 5945-6425 MHz |
| Argentina | 5925-7125 MHz |
| Australia | 5925-6425 MHz |
| Austria | 5945-6425 MHz |
| Azerbaijan | 5925-6425 MHz |
| Bahrain | 5925-6425 MHz |
| Bangladesh | 5925-6425 MHz |
| Belarus | 5945-6425 MHz |
| 5945-6425 MHz | |
| Belgium | 5945-6425 MHz |
| Bosnia and Herzegovina | 5945-6425 MHz |
| Brazil | 5925-7125 MHz |
| Bulgaria | 5945-6425 MHz |
| Burkina Faso | 5945-6425 MHz |
| Canada | 5925-7125 MHz |
| Chile | 5925-6425 MHz |
| Colombia | 5925-7125 MHz |
| Costa Rica | 5925-7125 MHz |
| Croatia | 5945-6425 MHz |
| Cyprus | 5945-6425 MHz |
| Czech Republic | 5945-6425 MHz |
| Denmark | 5945-6425 MHz |
| Dominican Republic | 5925-7125 MHz |
| Egypt | 5925-6425 MHz |
| El Salvador | 5925-7125 MHz |
| Estonia | 5945-6425 MHz |
| European Union | 5945-6425 MHz |
| Faroe Islands | 5945-6425 MHz |
| Finland | 5945-6425 MHz |
| France | 5945-6425 MHz |
| Georgia | 5945-6425 MHz |
| Germany | 5945-6425 MHz |
| Gibraltar | 5945-6425 MHz |
| Greece | 5945-6425 MHz |
| Guatemala | 5925-7125 MHz |
| Honduras | 5925-7125 MHz |
| Hong Kong | 5925-6425 MHz |
| Hungary | 5925-6425 MHz |
| Iceland | 5945-6425 MHz |
| India | 5945-6425 MHz |
| Ireland | 5945-6425 MHz 6425-7125 MHz |
| Isle of Man | 5945-6425 MHz |
| Italy | 5945-6425 MHz |
| Japan | 5925-6425 MHz 6425-7125 MHz |
| Jordan | 5925-6425 MHz |
| Kazakhstan | 5925-7125 MHz |
| Kenya | 5925-6425 MHz |
| Latvia | 5925-6425 MHz |
| Liechtenstein | 5945-6425 MHz |
| Lithuania | 5945-6425 MHz |
| Luxembourg | 5945-6425 MHz |
| Macao | 5945-6425 MHz |
| Macedonia | 5945-6425 MHz |
| Malaysia | 5925-6425 MHz |
| Malta | 5925-6425 MHz |
| Mauritius | 5925-6425 MHz |
| Mexico | 5925-6425 MHz |
| Moldova | 5925-6425 MHz |
| Monaco | 5945-6425 MHz |
| Montenegro | 5945-6425 MHz |
| Morocco | 5925-6425 MHz |
| Namibia | 5925-6425 MHz |
| Netherlands | 5945-6425 MHz 6425-7125 MHz |
| New Zealand | 5925-6425 MHz |
| Norway | 5945-6425 MHz |
| Pakistan | 5945-6425 MHz |
| Paraguay | 5925-6425 MHz |
| Peru | 5925-7125 MHz |
| Philippines | 5925-7125 MHz |
| Poland | 5925-7125 MHz |
| Portugal | 5945-6425 MHz 6425-7125 MHz |
| Qatar | 5925-6425 MHz |
| Romania | 5925-6425 MHz |
| Russian Federation | 5925-6425 MHz |
| San Marino | 5925-6425 MHz |
| Saudi Arabia | 5925-7125 MHz |
| Singapore | 5925-6425 MHz |
| Slovakia | 5925-6425 MHz |
| Slovenia | 5925-6425 MHz |
| South Africa | 5925-6425 MHz |
| South Korea | 5925-7125 MHz |
| Spain | 5945-6425 MHz |
| Sweden | 5945-6425 MHz |
| Switzerland | 5945-6425 MHz |
| Thailand | 5925-6425 MHz |
| Togo | 5925-6425 MHz |
| Tunisia | 5925-6425 MHz |
| Turkey | 5925-6425 MHz |
| Ukraine | 5925-6425 MHz |
| United Arab Emirates | 5925-6425 MHz |
| United Kingdom | 5945-6425 MHz |
| Holy See (Vatican City State) | 5945-6425 MHz |
| Vietnam | 5945-6425 MHz |
Compact, 2-port design
Like all ZenWiFi sets, the ZenWiFi BD4 includes identical mesh routers. Pick one as the primary unit (the rotuer) and the rest will work as satellites.
Each ZenWiFi BD4 mesh router shares the same shape and size as that of the ZenWiFi BD5—you literally can’t tell the two apart unless you look at the retail box or their underside, where the model names are. It’s the same design as previous Wi-Fi 7 hardware in the ZenWiFi family, but it is significantly smaller.
On the back, each ZenWiFi BD4 mesh router also has two auto-sensing 2.5Gbps Multi-Gig network ports. On the router (or primary) unit, the one that connects to the Internet source will work as the WAN port, and the other will work as a LAN. On a satellite unit, both work as a LAN, or you can use either as the uplink in a wired backhaul setup.
Considering the hardware’s entry-level Wi-Fi specs, the 2.5Gbps ports make sense in terms of real-world bandwidth. The table below shows how the ZenWiFi BD4 is stacked up against the ZenWiFi BD5 and the dual-band TP-Link Deco counterpart.
Hardware specifications: ASUS ZenWiFi BD4 vs. ASUS ZenWiFi BD5 vs. TP-Link BE3600
ZenWiFi BD4 vs. ZenWiFi BD5: The key difference
As noted on the table above, the only difference between the two dual-band ZenWiFi sets is the fact that the BD4 does not support the 240MHz channel width, whereas the BD5 does. The wider the channel, the higher the wireless bandwidth.
So how significant is this? That depends.
On the front end, all existing Wi-Fi 7 clients I’ve encountered don’t support the 240MHz channel width. They switch between 160MHz and 320MHz.
As a result, when you use these dual-band ZenWiFi sets with wired backhauling, or as a single router, there’s no difference between the two from a client’s perspective. Both will deliver the top theoretical speed of 2882Mbps on the 5GHz band.
Fronthaul vs. backhaul
When you use multiple Wi-Fi broadcasters—in a mesh Wi-Fi system or a combo of a router and an extender—there are two types of connections: fronthaul and backhaul.
Fronthaul is the Wi-Fi signals broadcast outward for clients or the local area network (LAN) ports for wired devices. It’s what we generally expect from a Wi-Fi broadcaster.
Backhaul (a.k.a backbone), on the other hand, is the link between one satellite Wi-Fi broadcaster and another, which can be the network’s primary router, a switch, or another satellite unit.
This link works behind the scenes to keep the hardware units together as a system. It also determines the ceiling bandwidth (and speed) of all devices connected to the particular satellite Wi-Fi broadcaster.
When a Wi-Fi band handles backhaul and fronthaul simultaneously, only half its bandwidth is available to either end. When a Wi-Fi band functions solely for backhauling, often available traditional Tri-band hardware, it’s called the dedicated backhaul.
Generally, for the best performance and reliability, network cables are recommended for backhauling—wired backhauling, which is an advantage of mesh Wi-Fi hardware with network ports. In this case, a satellite broadcaster can use its entire Wi-Fi bandwidth for front-hauling.
On the other hand, the ZenWiFi BD5 is clearly better than the ZenWiFi BD4 in a fully wireless setup. In this case, the 240MHz channel width is utilized in the former’s wireless backhaul link, allowing it to have up to 4324Mbps of theoretical bandwidth on the 5GHz, compared to 2882Mbps of the latter. A stronger backhaul means more bandwidth for the clients at the satellite unit.
If you’re wondering if you can mix the ZenWiFi BD4 and ZenWiFi BD5 in a single system, the answer is yes, but only when you use wired backhauling. More on that in the post linked below.
Another familiar ZenWiFi system
Other than the difference in Wi-Fi specs, the ZenWiFi BD4 proved to be identical to the ZenWiFi BD5 in my experience, including the fact that it’s among a few that don’t support universal backup and restore, meaning you can’t port the settings of an existing ASUS router onto it in an upgrade.
Overall, here’s what you can expect from it:
- The support for MLO: The hardware comes with MLO out of the box. When you get a pack and use the wireless mesh system, the hardware automatically uses an MLO link as the backhaul, dubbed “Smart Haul” by Asus. Note that MLO is only available as backhaul when the satellite unit connects directly to the primary router unit.
- Pre-synced hardware: When you get a pack, the identical hardware units are pre-synced. All you need to do is pick one unit to set up as the primary router—one of them comes with a removable “Main Unit” label for easy identification, though you can pick any—and the rest will be part of the system when plugged in.
- Part of the AiMesh family: Technically, the ZenWiFi BD4 can work with any AiMesh-enabled router (virtually all ASUS routers released since Wi-Fi 6) to form a Wi-Fi system. However, for the best performance, specific rules apply.
- ASUSWRT 5.0 firmware and core features:
- Multiple SSIDs via the “Smart Home Master” feature.
- Safe Browsing with DNS filters via specific servers.
- Useful Parental Controls and an advanced VPN feature set, which includes VPN Fusion and Instant Guard.
- Advanced QoS and online protection (via AiProtection) to keep your network and devices safe.
- A comprehensive set of network settings and features is managed via the web user interface or the (optional) ASUS Router mobile app, which requires no login account or subscription.
The gist is that if you’ve used an ASUS router before, the new ZenWiFi BD4 will be a familiar experience. It’s worth noting that, generally, it’s best to set it up using the web user interface and opt for the ASUS mobile app afterward for convenience.
Tip
Avoid using the ASUS mobile app for the setup process. The app is generic and lacks specifics applied to a particular Asus router. While this app might work in most cases and is convenient for monitoring your network, it can cause unknown and unexpected issues when used to set up new hardware or make specific changes to the system. If that’s your case, reset the hardware and set it up again using the web user interface before using the app if you can’t resist it.
ZenWiFi BD4: Reliable Gig+ performance with the latest firmware
As mentioned, for this review, I used the ZenWiFi BD4 for an extended period of time, months. Initially, the mesh set proved to be quite buggy with the initial firmware versions. However, with the latest one, it has been reliable.
It’s worth noting that I used it with wired backhaul, which is the only way you should use it, and the real-world data rates were almost identical to those of the ZenWiFi BD5. For this reason, I decided not to repeat the whole testing process, which would take me quite a bit of time. You can use the performance charts of the BD5 to get an idea of what you can expect.
Overall, considering the 2.5Gbps port and minimum Wi-Fi 7 specs, the ZenWiFi BD4 delivers speeds up to Gig+. So if you have Gigabit or lower broadband, it’ll work out well.
Pros
Dual-band Wi-Fi 7 with two 2.5Gbps ports and reliable performance, affordable
ASUSWRT 5.0 has lots of customizations and free-for-life high-end features (VPN, Parental Controls, Online Protection, Smart Home Master, etc.).
Robust web user interface and helpful optional mobile app; easy-to-blend-in design
Compact with no internal fan
Cons
Only two network ports; bare-minimum Wi-Fi 7 specs
The takeaway
The ASUS ZenWiFi BD4 is not earth-shattering, but it has enough to deliver Gigabit-class, even Gig+, real-world performance, especially when used in a wired home. That, plus the comprehensive set of features known among ASUS’s ZenWiFi hardware, makes it a formidable contender among the dual-band Wi-Fi 7 mesh crowd. Consider one today!
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