IPv6 and DNS Lead to Some Slow Websites

  • I have a Dell Optiplex 990 computer with a Quad-port 82575GB Gigabit Network Connection NIC running PFsense 2.4.4. It is configured with IPv4 and IPv6 from my WAN provider in which it is providing an IPv6 prefix for my internal network. I am also using DNS Resolver for local DNS on my network. I have configured my PFsense box to have Google DNS and One DNS but have also allowed ISP to override them.

    Most websites I access come up just fine. However, I have a hand full of websites that are incredibly slow to bring up or do not bring up completely (missing CSS, pictures, ads and more). I connected my PC directly to my modem and the sites pull up just fine. I connected my router back up. Then on my host, I assigned DNS to Google's DNS server and still slow. Then I disabled IPv6 on my host and BOOM, it works! Any combination of the two does not work unless DNS on my host is to something other than PFSense and IPv6 is disabled on my host.

    At this point, I am unaware of where to go next. Should I turn IPv6 off on my PFSense box and not use DNS Resolver? I rather not since I like to have IPv6 functionality and DNS Resolver offers internal DNS for my hosts and devices. Is there any logs I can check further into or any options that might help?

    • BIOS
      Vendor: Dell Inc.
      Version: A23
      Release Date: Sun Feb 11 2018

    • Version
      2.4.4-RELEASE (amd64)
      built on Thu Sep 20 09:03:12 EDT 2018
      FreeBSD 11.2-RELEASE-p3
      Version information updated at Tue Oct 2 10:02:18 CDT 2018

    • CPU Type
      Intel(R) Core(TM) i5-2400 CPU @ 3.10GHz
      Current: 3100 MHz, Max: 3101 MHz
      4 CPUs: 1 package(s) x 4 core(s)
      AES-NI CPU Crypto: Yes (active)

    • Hardware crypto

    • Kernel PTI

    • Uptime
      01 Hour 19 Minutes 42 Seconds

    • Current date/time
      Tue Oct 2 11:21:16 CDT 2018

    • DNS server(s)

    • Installed Packages:
      LADVD 1.2.2
      mailreport 3.3
      mtr-nox11 0.85.6_1
      nmap 1.4.4_1
      open-vpn-export 1.4.17_2
      RRD_Summary 2.0
      Service_Watchdog 1.8.6
      Status_Traffic_Totals 1.2.4
      sudo 0.3_1

  • Update:

    I enabled IPv6 on my host and assigned it a static IPv6 DNS Address of 2606:4700:4700::1001 ( DNS) and it worked.

    So as of right now, the websites that are slow work just fine if I set my IPv4 and IPv6 DNS server entries to something other than my local pfsense router.

    Still do not know why that should matter or what the fix for DNS Resolver should be.

  • Out of curiosity, what do you see for the MTU of your WAN interface under status/interfaces?

  • Temporarily, I have resolved the issue by changing from DNS Resolver to to DNS Forwarder. However, I rather have the local DNS server myself that using external DNS servers. So I'm still looking into this.

    Below are the stats for my WAN connection. NOTE: Even though the MTU says 9000, the largest ping I can get from Windows to the Default Gateway of my WAN is 1472. I can ping with jumbo frames to the LAN interface and any object within my LAN

    WAN Interface (wan, igb0)

    • Status

    • DHCP
      up Relinquish Lease

    • MAC Address
      00:1b:21:3c:42:40 - Intel Corporate

    • IPv4 Address

    • Subnet mask IPv4

    • Gateway IPv4

    • IPv6 Link Local

    • IPv6 Address

    • Subnet mask IPv6

    • Gateway IPv6

    • DNS servers

    • MTU

    • Media
      1000baseT <full-duplex>

    • In/out packets
      1638176/805107 (1.89 GiB/94.49 MiB)

    • In/out packets (pass)
      1638176/805107 (1.89 GiB/94.49 MiB)

    • In/out packets (block)
      6670/0 (782 KiB/0 B)

    • In/out errors

    • Collisions

  • Try refreshing the connection without manually setting anything for the WAN MTU, and and please report what the MTU gets set to as reported in status/interfaces.

  • It reports my MTU as 1500

  • Try testing your IPv6 connectivity and DNS lookup with the MTU set to default on the WAN. Do you still have the same problems?

  • No Go. I just switched back to DNS Resolver and still some websites are slow. As soon as I switch back to DNS Forwarder, they work fine.

  • What are your settings in DNS Resolver?

  • Any easy way to get that other than a screen shot?

  • ICMP blocked somewhere?
    Maybe Prefer IPv4 over IPv6 helps?

  • You should leave the WAN MTU at the default. Being able to send a max ping of 1472 shows that 1500 is your actual MTU on the connection. The missing 8 bytes are the ICMP header for the ping packets. Please report what you have set for "IP Do-Not-Fragment compatibility", in system/advanced/firewall&nat?

  • @pippin Under system i did specify for it to use IPv4 over IPv6 but sadly didn't change anything

  • A screenshot of the first settings page would be perfect.

  • @bfeitell I have the IP Don-Not-Fragment compatibility flag not set. Should I enable that feature?

  • I would try it, and see if it has an effect on the function of DNS Resolver. I think that playing with your MTU on the WAN might be the cause, but I'd still like to see your settings for DNS Resolver. If you are using dns over tls with the Quad9 resolvers, that might explain things. I have found the Quad9 resolvers to be very slow in comparison to the cloudflare resolvers.

  • Below are the basic settings I have for DNS Resolver:

    0_1538518269334_DNS Resolver Settings.png

  • Check the log file for DNSBL in pfblocker. Depending upon what lists you are using, you might be blocking access to certain name servers you need for DNS Resolver to work correctly. If you temporarily disable pfb_dnsbl, you will need to reload on the update page to clear any blocks. Then test the DNS Resolver again.

  • Pfblockerng isn't much of the issue. I factory reset my router and did a minimal setup using DNS Resolver and no pfblockerng. Still had the same issue. After seeing no change, I restored my original config bringing pfblockerng back

  • @wre136 I bet on https://redmine.pfsense.org/issues/8934 have own DNS on FreeBSD and get many problems with IPv6 DNS and Fragments. Disabling scrubbing helps. But then IPv4 DNS has same problems :-(

    Oct  9 17:25:41 host1 kernel: ipfw: 65300 Deny TCP [2001:500:e::1] [2axx:xxxx:xxxx:xxxx::53] in via bge0 (frag 1217fb81:188@9856)
    Oct  9 17:25:57 host1 kernel: ipfw: 65300 Deny TCP [2001:500:f::1] [2axx:xxxx:xxxx:xxxx::53] in via bge0 (frag 4d6091d8:188@9856)
    Oct  9 17:26:45 host1 kernel: ipfw: 65300 Deny TCP [2001:500:e::1] [2axx:xxxx:xxxx:xxxx::53] in via bge0 (frag 350be3db:188@9856)
    Oct  9 17:31:29 host1 kernel: ipfw: 65300 Deny UDP [2001:500:40::1] [2axx:xxxx:xxxx:xxxx::53] in via bge0 (frag b576286c:361@9856)
    Oct  9 17:51:24 host1 kernel: ipfw: 65300 Deny UDP [2001:470:1a::1] [2axx:xxxx:xxxx:xxxx::53] in via bge0 (frag 8533c2a5:642@9856)
    Oct  9 17:51:26 host1 kernel: ipfw: 65300 Deny UDP [2001:5a0:10::1] [2axx:xxxx:xxxx:xxxx::53] in via bge0 (frag e06893c2:650@9856)
    Oct  9 17:53:07 host1 kernel: ipfw: 65300 Deny UDP [2001:67c:18c4:2000::11:53] [2axx:xxxx:xxxx:xxxx::53] in via bge0 (frag 55df3089:362@9856)
    Oct  9 18:11:05 host1 kernel: ipfw: 65300 Deny UDP [2001:500:48::1] [2axx:xxxx:xxxx:xxxx::53] in via bge0 (frag 8424932b:361@9856)
    Oct  9 18:11:25 host1 kernel: ipfw: 65300 Deny UDP [2001:500:b::1] [2axx:xxxx:xxxx:xxxx::53] in via bge0 (frag 9da68734:361@9856)
    Oct  9 18:14:41 host1 kernel: ipfw: 65300 Deny UDP [2001:500:c::1] [2axx:xxxx:xxxx:xxxx::53] in via bge0 (frag 69a41126:361@9856)
    Oct  9 18:18:05 host1 kernel: ipfw: 65300 Deny UDP [2001:500:40::1] [2axx:xxxx:xxxx:xxxx::53] in via bge0 (frag a639e4fd:361@9856)

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