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So I've recently acquired a wireless repeater (Asus RP-AC55) because my router didn't reach everywhere I needed it to, but so far it has introduced a bigger issue than the one it was supposed to fix.

The main part issue is that it simply won't allow any Ubuntu device to connect to it. I've tried with 2 different laptops (two Zenbooks) + 1 old desktop on two different versions of Ubuntu (16.04 and 18.04) (none of those have had given me WiFi related issues prior to this), and it absolutely won't work with any of them. One of the Zenbooks has a Windows partition installed and the connection to the router works seamlessly when using Windows. I've also tried a few Android phones and all of them are able to connect to the repeater (and to the internet through it) without any issue.

The second part is that, when attempting to connect to the repeater from one of the Ubuntu-based devices, the repeater will simply crash, shutdown and reboot. For a few seconds there will be a question mark in the wireless indicator (running GNOME Shell by the way) and no access to the internet, and then the connection drops and the repeater reboots.

After a bit more experimentation, I'm think it's at least partly a DNS issue: If I set an IP address manually, my laptop connects to the router and it doesn't crash , and ping 8.8.8.8 in the terminal gives positive results, but nslookup and normal internet browsing fails.

If I leave the IP address setting to "Automatic (DHCP)", it still crashes but on top of that trying to ping anything (before the crash) fails. I tried to set the DNS manually to Google's DNS (8.8.8.8, 8.8.4.4) (on top of setting a manual IP) for the connection to the repeater, but if I do that it crashes like it would if I didn't set the IP manually and nothing pings. I've also tried to set the repeater itself to Google's DNS, but that didn't bring any positive result either.

So I guess the issue is both with DNS and obtaining an IP, the first one of which I have no clue how I can "fix".

I'm willing to provide any logs you might need as long as I manage to get them (the near immediate reboot might make some logs rather hard to obtain), but as I don't know which ones might be useful I haven't included any in this post.

Hope someone will be able to help me fix my problem, and thanks in advance to those who will try.

5 Answers 5

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As mentioned by others, the issue is related to DNS queries. Disabling systemd-resolved is a good solution.

The following fix works with Ubuntu 18.04LTS and Asus RP-AC55 with firmware 3.0.0.4.384_83130.


On the Linux device, do the following:

  1. Disable systemd-resolved:

    sudo systemctl disable --now systemd-resolved
    
  2. Remove the resolv.conf file:

    sudo rm /etc/resolv.conf
    
  3. In NetworkManager.conf's [main] block add the line dns=default:

    sudo nano /etc/NetworkManager/NetworkManager.conf
    
    # Move cursor to a newline inside the [main] block and insert the line below
    dns=default
    

    Save the file afterwards.

  4. Restart NetworkManager:

    sudo systemctl restart NetworkManager
    

On the repeaters website do the following:

  1. Go to Advanced Settings/Lan and set Get LAN IP Automatically? to No
  2. Set the DNS Server1 and DNS Server2 fields to your preferred DNS servers, eg. 8.8.8.8 and 1.1.1.1.
  3. Reboot the repeater.

Once both things have been configured, try on the Linux device to use the repater's network. Should be working just fine.

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DNS query for AAAA with an OPT record causes the crash and reboot of the RP-AC55. I reported the issue to the support (we will see the outcome) but you may disable OPT as a workaround for now.

/etc/resolv.conf is managed by the systemd-resolved service. Best would be to disable OPT at its level but I doubt it's possible so..

  1. # systemctl disable --now systemd-resolved

  2. # mv /etc/resolv.conf /etc/resolv.conf_back

  3. # systemctl restart NetworkManager.service

  4. After a while you should /etc/resolv.conf file without options edns0 and nameserver you need.

If you want to experiment more:

# apt-get install tcpreplay wireshark
# echo 1MOyoQIABAAAAAAAAAAAAP//AAABAAAAF5KkXEZEAwBVAAAAVQAAAAAIogvECTBSy4RecQgARQAARxPgQABAEQrlCgAB0ggICAictgA1ADOaBkTsAQAAAQAAAAAAAQN3d3cGZ29vZ2xlA2NvbQAAHAABAAApBLAAAAAAAAA= | base64 -d > asus-rp-ac55-DoS.pcap

To crash the router run:

# tcpreplay -L 1 --intf1 wlp58s0 asus-rp-ac55-DoS.pcap

To see what's inside of the packet:

# wireshark -r asus-rp-ac55-DoS.pcap
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OK, my previous post was deleted, probably because it didn't really contain any valuable info more than my findings up to that moment. I can now verify that I have found a better workaround for the problem!

I run my 3 RP-AC55 in AP-mode, and I haven't been able to use them with my Ubuntu laptop due to the same reboot problem as @philippe-lepaffe. I have worked really hard trying to find a nvram setting that would disable dnsmasq since it should be that daemon that catches the AAAA OPT request which crashes the Repeater. I have found no such solution, but after reading up on ASUSWRT-Merlin I found somewhat similar problems and those were solved by putting the router in static IP-mode, thereby disabling the DHCP-part of dnsmasq and putting 2 DNS-servers in the settings, and disable "Connect to DNS Server automatically". This seems to do the trick for RP-AC55 too! So, put a static IP for the repeater (and manual DNS servers) instead of DHCP, and the reboots go away!

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The latest firmware update Version 3.0.0.4.384.83394 from ASUS fixes this issue:

https://www.asus.com/Networking-IoT-Servers/Range-Extenders-/All-series/RP-AC55/HelpDesk_BIOS/

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Updating the repeater firmware to the latest version did work for me. You can find it here: https://www.asus.com/me-en/supportonly/rp-ac55/helpdesk_bios?model2Name=RP-AC55

My version was something like 3.0.0.4.382, I updated to 3.0.0.4.384.83577 since the changelog says that they have improved stability. The repeater no longer reboots when connecting my ubuntu computer to it!

Also, this video can help you update the firmware: https://www.youtube.com/watch?v=hs_HfDZeCqY

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