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I have a wireless home network set up around a router that I upgraded from OpenWRT 19.07 to 21.02.1 a couple of weeks ago. Two devices are connected to the router wirelessly, both of which are able to access the Internet, and either can also connect via SSH to the router itself. I am however unable to establish an SSH connection from one device to the other; attempting to do so returns an error message ‘No route to host’. A ping from one to the other returns ‘Destination Host Unreachable’.

Name resolution works correctly: both devices’ names resolve to their local IPv4 addresses. I can also connect to either device from the router. Strangely, I am also able to establish an SSH connection between one device connected via a wired Ethernet connection and another connected wirelessly.

I remember this working fine back when I was running 19.07. How can I possibly diagnose or fix this?

user3840170
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  • do you have any client/AP isolation features enabled on OpenWRT? they prevent wifi devices from talking to each other, so that people don't try to hack or sniff traffic from other systems on the wireless lan. – Frank Thomas Nov 29 '21 at 19:16
  • @FrankThomas I don’t think I enabled anything; I mostly copied `/etc/config` files verbatim from before the upgrade. How do I check, though? Preferably from the command line, I have the web interface disabled to save memory. – user3840170 Nov 29 '21 at 21:57
  • Following , I did `echo 1 > /sys/devices/virtual/net/br-lan/lower_wlan0/brport/hairpin_mode`, and it started working. Now how do I make it permanent? – user3840170 Nov 29 '21 at 22:08
  • hairpin huh. that's interesting, I'm no OpenWRT expert, but from that same thread, someone mentioned the Isolate setting in the file /etc/config/wireless. what is your `isolate` setting set to? – Frank Thomas Nov 29 '21 at 22:44
  • Unset. But when I disabled `multicast_to_unicast`, as suggested in , it seems to have helped. – user3840170 Nov 29 '21 at 23:05
  • What's the status of the setting `ap_isolate` in hostapd on your OpenWRT system? See also this Q/A (where indeed hairpin is used): https://superuser.com/questions/1661060/hostapd-how-to-block-only-netbios-broadcasts-to-clients-in-same-wlan-by-applyin – A.B Dec 13 '21 at 14:30
  • My `/var/run/hostapd-phy0.conf` has `ap_isolate=1`. But with `option multicast_to_unicast 0` in `/etc/config/wireless` routing works fine now, I just didn’t write it down as an answer. – user3840170 Dec 13 '21 at 14:39

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