I recently updated the firmware on my ASUS RT-AX58U router to the latest version hoping to fix some connectivity quirks. One big reason was to get proper guest network isolation working - I want guests to access the internet but not see my main devices. However, after the update, devices on the guest network still seem to ping or access shared folders on my main network, which is a security no-no for me. I’ve double-checked the guest network settings to ensure isolation is enabled and even reset the router to factory defaults before reconfiguring. I also tried toggling AP isolation and tested with multiple devices (phones, a laptop). The router’s admin page shows guest isolation as active, but in practice, devices can still 'see' each other across networks. Has anyone else had problems with guest network isolation not working properly on ASUS routers after a firmware update? Is there a hidden setting or workaround to truly lock down guest access? Would switching to a third-party firmware like Merlin be worth the hassle for this? I want to keep the main network secure without buying new hardware if possible.

On 02/07/2026 at 1:50 PM, techbloke said:

I recently updated the firmware on my ASUS RT-AX58U router to the latest version hoping to fix some connectivity quirks. One big reason was to get proper guest network isolation working - I want guests to access the internet but not see my main devices. However, after the update, devices on the guest network still seem to ping or access shared folders on my main network, which is a security no-no for me. I’ve double-checked the guest network settings to ensure isolation is enabled and even reset the router to factory defaults before reconfiguring. I also tried toggling AP isolation and tested with multiple devices (phones, a laptop). The router’s admin page shows guest isolation as active, but in practice, devices can still 'see' each other across networks. Has anyone else had problems with guest network isolation not working properly on ASUS routers after a firmware update? Is there a hidden setting or workaround to truly lock down guest access? Would switching to a third-party firmware like Merlin be worth the hassle for this? I want to keep the main network secure without buying new hardware if possible.

@techbloke, that sounds super frustrating - guest isolation should be straightforward but sometimes these firmware updates mess with the settings under the hood. Since you’ve already factory reset and double-checked isolation toggles, it might be worth diving into the router’s LAN settings to see if there’s any VLAN or subnet overlap causing the bleed-through. Sometimes the guest network shares the same subnet or lacks proper firewall rules, letting devices peek across.

Switching to Merlin firmware is often recommended for ASUS routers because it gives you more control over firewall rules and VLANs, which can really lock down guest access. It’s a bit of a hassle to flash and configure, but if you’re comfortable with a bit of tinkering, it could solve your problem without buying new hardware. Just make sure to back up your current config before flashing!

On 02/07/2026 at 1:50 PM, techbloke said:

I recently updated the firmware on my ASUS RT-AX58U router to the latest version hoping to fix some connectivity quirks. One big reason was to get proper guest network isolation working - I want guests to access the internet but not see my main devices. However, after the update, devices on the guest network still seem to ping or access shared folders on my main network, which is a security no-no for me. I’ve double-checked the guest network settings to ensure isolation is enabled and even reset the router to factory defaults before reconfiguring. I also tried toggling AP isolation and tested with multiple devices (phones, a laptop). The router’s admin page shows guest isolation as active, but in practice, devices can still 'see' each other across networks. Has anyone else had problems with guest network isolation not working properly on ASUS routers after a firmware update? Is there a hidden setting or workaround to truly lock down guest access? Would switching to a third-party firmware like Merlin be worth the hassle for this? I want to keep the main network secure without buying new hardware if possible.

Sounds frustrating that the guest isolation isn’t kicking in despite the settings showing active. The RT-AX58U’s stock firmware can be a bit hit-or-miss with guest network segmentation, especially after updates that might tweak how isolation rules are applied. Sometimes the “guest network” is just a VLAN with access rules that don’t fully block LAN access as expected.

Switching to Asuswrt-Merlin often helps because it gives you more granular control over firewall rules and VLANs, letting you explicitly block traffic between guest and main networks. It’s not too painful to install and revert if needed, and I’ve found it worth the effort for better security and stability. Just make sure to back up your current config before flashing.

In the meantime, you might want to double-check if any shared folders are set to “public” or if there’s any UPnP or multicast forwarding enabled that could leak visibility across networks. Sometimes those little settings

@techbloke, it’s frustrating when the guest isolation feature shows as enabled but doesn’t actually block access like it should. On my RT-AX58U, I noticed that sometimes the isolation only applies to wireless guests and not wired ones, so double-check if your guest devices are connecting via Ethernet or Wi-Fi. Also, some firmware updates introduce bugs that can cause this kind of issue, so switching to Merlin firmware helped me get more reliable guest isolation and extra controls without new hardware.

That said, if you're not comfortable flashing third-party firmware, a quick workaround I use is setting up VLANs if your router supports it, which adds a more robust layer of separation. Worth exploring before diving into Merlin, especially since you want to keep things secure without extra gear.

On 02/08/2026 at 4:40 AM, ChattyChuckle said:

On 02/07/2026 at 1:50 PM, techbloke said:

I recently updated the firmware on my ASUS RT-AX58U router to the latest version hoping to fix some connectivity quirks. One big reason was to get proper guest network isolation working - I want guests to access the internet but not see my main devices. However, after the update, devices on the guest network still seem to ping or access shared folders on my main network, which is a security no-no for me. I’ve double-checked the guest network settings to ensure isolation is enabled and even reset the router to factory defaults before reconfiguring. I also tried toggling AP isolation and tested with multiple devices (phones, a laptop). The router’s admin page shows guest isolation as active, but in practice, devices can still 'see' each other across networks. Has anyone else had problems with guest network isolation not working properly on ASUS routers after a firmware update? Is there a hidden setting or workaround to truly lock down guest access? Would switching to a third-party firmware like Merlin be worth the hassle for this? I want to keep the main network secure without buying new hardware if possible.

@techbloke, that sounds super frustrating - guest isolation should be straightforward but sometimes these firmware updates mess with the settings under the hood. Since you’ve already factory reset and double-checked isolation toggles, it might be worth diving into the router’s LAN settings to see if there’s any VLAN or subnet overlap causing the bleed-through. Sometimes the guest network shares the same subnet or lacks proper firewall rules, letting devices peek across.

Switching to Merlin firmware is often recommended for ASUS routers because it gives you more control over firewall rules and VLANs, which can really lock down guest access. It’s a bit of a hassle to flash and configure, but if you’re comfortable with a bit of tinkering, it could solve your problem without buying new hardware. Just make sure to back up your current config before flashing!

@techbloke, it sounds like the guest isolation feature might be bugged in that latest firmware if it’s showing as enabled but not actually blocking traffic. I had a similar issue on an ASUS router where the guest network could still see some devices on the main LAN after an update. Switching to Merlin firmware fixed it for me because it gives more granular control over firewall rules and isolation. It’s a bit of a learning curve but definitely worth it if you want true separation without buying new gear.

Also, double-check if there’s any “allow LAN access” option buried in the guest network settings - sometimes that’s enabled by default or reset after updates. If you want to avoid third-party firmware, you might try manually adding firewall rules to block inter-VLAN traffic, but that’s more advanced. Merlin’s community forums are pretty helpful if you go that route.

@cc704, you nailed the frustrating part - when the router shows isolation enabled but devices still peek into the main network, it’s like a ghost in the machine. From what I’ve seen with the RT-AX58U, the guest network isolation sometimes doesn’t fully cut off Layer 2 traffic, especially if the firmware update introduced some subtle bug or regression.

One trick that helped me was disabling “Multicast forwarding” and “IGMP Snooping” under the LAN settings. It’s not obvious, but those can leak traffic between VLANs or SSIDs even if isolation is on. Also, double-check if your guest network is set to use a different subnet; sometimes isolation depends on that separation.

Regarding Merlin firmware, it’s a solid choice if you’re comfortable flashing and want more granular control. It fixed similar issues for me on an ASUS router, but it’s not for everyone. If you want to avoid that, try the multicast