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Setup:

  • router TL-WR841N (tp-link last firmware TL-WR841N v13 00000013)
  • laptop (macOS)
  • Raspberry Pi 4 (Raspberry Pi OS)

IPs assigned successfully via DHCP router service. Disabled "SSID broadcast" in router settings for security reasons. SSH, ping and arp resolving does not work via the router between devices.

When enabling SSID broadcast back - it becomes possible to ping, and connect to rpi via ssh from laptop.

Why may setting of "SSID broadcast" affect communication between connected devices inside LAN within one subnet?

UPD 1.

After enabling and disabling SSID broadcast back - strange enough, it became possible to ping and ssh to rpi. Maybe something like arp data cached, when I tried to connect to rpi with enabled ssid broadcast.

But, now I am trying to ping another connected device (phone) in WLAN (that I did not ping with enabled SSID broadcast) and getting

ping 192.168.0.102                                                                                                                                                                         
PING 192.168.0.102 (192.168.0.102): 56 data bytes
Request timeout for icmp_seq 0
Request timeout for icmp_seq 1
Request timeout for icmp_seq 2

After 1 minute, ping started working to that phone too...

ping 192.168.0.102                                                                                                                                                                         
PING 192.168.0.102 (192.168.0.102): 56 data bytes
64 bytes from 192.168.0.102: icmp_seq=0 ttl=64 time=308.295 ms
64 bytes from 192.168.0.102: icmp_seq=1 ttl=64 time=122.725 ms
64 bytes from 192.168.0.102: icmp_seq=2 ttl=64 time=124.204 ms

So it really might be related to an unstable network?

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  • 1
    Keep in mind that hiding the SSID broadcast does not improve security.
    – Daniel B
    Commented Sep 30, 2021 at 11:47

1 Answer 1

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1

SSID broadcast on or off has NOTHING to do with SSH, ping, arp.

What I think really happens is that either your PI or your laptop looses Wifi connection when SSID broadcast is disabled, because it is not properly configured to connect when the SSID is not visible.

I don't know what OS your PI is using but your laptop, if it is using Windows, needs a "manual" Wifi connection (For W10: Wi-Fi in Settings, Manage Known Networks and than "Add a new connection") to be defined for the non-broadcasting SSID or it won't connect at all (and will loose connection if it was connected before SSID broadcast got disabled).

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  • I setup wifi connection on both targets - so I can use WAN w/o any problem. But, when I trying to ping target with Raspberry Pi OS via its assigned IP address from macOS laptop, wireshark shows me, that ARP requests have no responses. So, router does nothing with these broadcast packets.
    – yunir
    Commented Sep 30, 2021 at 11:22
  • 2
    @yunir That is weird... That almost sounds like your router automatically enables "wireless client isolation" when SSID broadcast is disabled. Which sort of makes sense, but which is something you don't want in this instance. See if you can switch that off manually in the router. It is called "Enable Client Isolation: in teh Wireless Advanced settings. Guest Wifi network has separate setting for it in teh Guest netowrk properties.
    – Tonny
    Commented Sep 30, 2021 at 11:43
  • Activate Client Isolation and Deny Ping packets from LAN port are disabled. So, it might be related to unstable network, but how to fix it? I've updated my question with UPD. 1 where we can see that it is about 100-300 ms to transmit simple icmp packet.
    – yunir
    Commented Sep 30, 2021 at 15:10

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