Netgate Discussion Forum
    • Categories
    • Recent
    • Tags
    • Popular
    • Users
    • Search
    • Register
    • Login

    DNS forwarder - WLAN on its own Subnet - CPU 100%

    Scheduled Pinned Locked Moved DHCP and DNS
    6 Posts 2 Posters 2.5k Views
    Loading More Posts
    • Oldest to Newest
    • Newest to Oldest
    • Most Votes
    Reply
    • Reply as topic
    Log in to reply
    This topic has been deleted. Only users with topic management privileges can see it.
    • ?
      A Former User
      last edited by

      I have a strange problem..

      I am using a domain name what resolved to a public IP from outside, on my LAN it resolves to a local IP.

      My setup looks like this:

      PFSENSE BOX IP: 10.10.1.254

      GENERAL SETUP
      –------- --------
      hostname: fw
      domain: example.com

      INTERFACES

      WAN ISP-IP
      LAN 10.10.1.254/24
      WLAN 10.10.2.254/24

      DNS SERVER


      208.67.222.222
      208.67.220.220

      [OFF] Allow DNS server list to be overridden by DHCP/PPP on WAN
      [OFF] Do not use the DNS Forwarder as a DNS server for the firewall

      DHCP SERVER
      –--- ----------
      [OFF] WAN
      [ON] LAN 10.10.1.125 - 10.10.1.250
      [ON] WLAN 10.10.2.125 - 10.10.2.250

      DNS FORWARDER
      –--- --------------
      [ON] Enable DNS forwarder
      [ON] Register DHCP leases in DNS forwarder

      Host Overrides
      example.com  10.10.1.100

      Domain Overrides
      example.com  10.10.1.254

      If I connect to my network via a network cable, everything runs fine.

      If I connect to my network via wireless, my cpu hits 100%

      If I turn off DNS Forwarding the cpu goes back to normal?

      If I bridge LAN & WLAN, the cpu is normal.

      I don't want to bridge LAN & WLAN, I want to keep them separate with appropriate firewall rules.

      Why is DNS Forwarding / dnsmasq hitting 100% when I connect to my network via wireless?
      Something to do with the wireless subnet causing dnsmasq to create some kind of DNS loop maxing out the CPU?

      1 Reply Last reply Reply Quote 0
      • W
        wallabybob
        last edited by

        Imagine something on your wireless network looks up www.example.com. Your DNS forwarding configuration says anything on domain example.com DNS forwarder doesn't know about should go to 10.10.1.254 which is the LAN interface. I don't know the intricacies of DNS forwarder but it seems to me that you have likely created an infinite loop: DNS forwarder should ask itself to resolve domain example.com. but that is unlikely to terminate EXCEPT for names fw.example.com and example.com.

        1 Reply Last reply Reply Quote 0
        • W
          wallabybob
          last edited by

          The netmask in the following items seems bizarre:
          @wizbit:

          INTERFACES
          –------------
          WAN ISP-IP
          LAN 10.10.1.254/0
          WLAN 10.10.2.254/0

          1 Reply Last reply Reply Quote 0
          • ?
            A Former User
            last edited by

            @wallabybob:

            The netmask in the following items seems bizarre:
            @wizbit:

            INTERFACES
            –------------
            WAN ISP-IP
            LAN 10.10.1.254/0
            WLAN 10.10.2.254/0

            That was a typo!! Changed now.

            1 Reply Last reply Reply Quote 0
            • ?
              A Former User
              last edited by

              @wallabybob:

              Imagine something on your wireless network looks up www.example.com. Your DNS forwarding configuration says anything on domain example.com DNS forwarder doesn't know about should go to 10.10.1.254 which is the LAN interface. I don't know the intricacies of DNS forwarder but it seems to me that you have likely created an infinite loop: DNS forwarder should ask itself to resolve domain example.com. but that is unlikely to terminate EXCEPT for names fw.example.com and example.com.

              If i connect to my network via LAN (network cable) to 10.10.1.254/24, DNS Forwarder seems to be running OK, CPU usage is normal. The problem only occurs when i connect to my network via Wireless what uses the 10.10.2.254/24 network. My state table fills up and my CPU goes 100%, if i turn off DNS Forwarder / dnsmasq, the CPU goes back to normal.

              1 Reply Last reply Reply Quote 0
              • ?
                A Former User
                last edited by

                PROBLEM SOLVED!!!

                My state table had LOTS of this:

                tcp 10.10.2.30:53227 -> 10.10.1.100:631 FIN_WAIT_2:FIN_WAIT_2

                CUPS was sending LOTS of requests,  I added the 10.10.2. network to CUPS on my
                server and now everything is back to normal!  :)

                1 Reply Last reply Reply Quote 0
                • First post
                  Last post
                Copyright 2025 Rubicon Communications LLC (Netgate). All rights reserved.