Why can't I ping or connect to another device on a different WiFi band?

milesuy · January 3

My laptop and phone can't ping and connect to the printer when they are connected to the 5GHz band, but pings and connects when it is on the 2.4GHz. I tried connecting the printer in the 5GHz band and this time my devices can't connect to the printer when they are in 2.4GHz. Although I have a desktop PC that is connected via LAN (Wired) and it can connect to the printer regardless whether the printer is in the 2.4GHz or 5GHz band. When pinging the printer the error I get is Destination Host Unreachable and the HP Smart app can't find the printer. I am also unable to ping other devices that are on a different band (Ex: Laptop in 5GHz and phone in 2.4GHz), but I am able to ping devices on LAN (Wired) (Ex: Desktop in LAN and phone in 5GHz). The router is a DrayTek Vigor 2915ac. I am using the same subnet 192.168.2.1/24 on all networks (2.4GHz, 5GHz, and Wired LAN), Isolate Member and VLAN are also disabled.

Why can't I ping or connect to another device on a different WiFi band? What am I missing?

Gorgon · January 3

Likely there is an issue with the Bridging configuration. It sounds like the LAN (wired network) can forward packets to both the 2.4 and 5GHz Bridge Groups but the Bridge Groups aren't configured to allow forwarding to each other or likely also to the LAN.

Here is my router using FreshTomato:

The above basically allows the LAN (bridge0) to talk to the WiFi (Bridge1). If I wanted the WiFi to talk to the LAN I'd have to add a policy allowing Src: br1 to Dest:br2.

Under the hood, most routers use Linux and thus IPtables and all these rules do is allow Layer 2 forwarding of packets between Bridge Groups.

milesuy · January 3

31 minutes ago, Gorgon said:

Likely there is an issue with the Bridging configuration. It sounds like the LAN (wired network) can forward packets to both the 2.4 and 5GHz Bridge Groups but the Bridge Groups aren't configured to allow forwarding to each other or likely also to the LAN.

Here is my router using FreshTomato:

The above basically allows the LAN (bridge0) to talk to the WiFi (Bridge1). If I wanted the WiFi to talk to the LAN I'd have to add a policy allowing Src: br1 to Dest:br2.

Under the hood, most routers use Linux and thus IPtables and all these rules do is allow Layer 2 forwarding of packets between Bridge Groups.

I don't have an issue with the connection between LAN to WiFi. My issue is the connection between 2.4GHz and 5GHz.

I am able to ping a Desktop PC on Ethernet (Wired) from my phone on WiFi (Wireless) and vice versa, but if I used my laptop in 2.4GHz WiFi to ping my phone in 5GHz WiFi and vice versa, it fails.