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  1. #1

    DNS settings for routers

    Model :

    Hardware Version :

    Firmware Version :

    ISP : [/COLOR]

    Just set up with a DSL connection and was looking at configuration.

    This is Frontier and looking in the gateway setup it is using dynamic DNS.

    I read about Goggle DNS and I changed the setting on this computer I'm using as this is the one I actually surf on.

    Other computers just watch Netflix etc.

    It makes loading pages quicker than before for sure, I was experiencing some good 5 second lags before pages loaded.

    Should I use that on my CPE's that I use between this computer and the gateway?

    Maybe just on the ones connected to the gateway?

    Just curious about DNS, it's just blank on all my CPE settings.

    Thanks

    I'm using 8.8.8.8

  2. #2
    Members R1D2 is on a distinguished road
    Join Date
    Dec 2015
    Posts
    1,636
    If your gateways DNS is slower than Google DNS, it is either doing a recursive lookup (small time difference only) or probably overloaded at the ISP (huge time difference).

    Usually, ISPs set up caching DNS servers, which are - by network topology - "nearer" then any DNS in the Internet. Of course, you can set up such a caching server for yourself inside your own network, e.g. on your router (if it supports setting up a full DNS) or a dedicated server.

    For example, if looking up the domain tp-link.us, querying Google's DNS took 45ms:

    Code:
    $ dig tp-link.us @8.8.8.8
    ; <<>> DiG 9.9.5-9+deb8u15-Debian <<>> tp-link.us @8.8.8.8
    ;; global options: +cmd
    ;; Got answer:
    ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 28362
    ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
    
    
    ;; OPT PSEUDOSECTION:
    ; EDNS: version: 0, flags:; udp: 512
    ;; QUESTION SECTION:
    ;tp-link.us.            IN    A
    
    
    ;; ANSWER SECTION:
    tp-link.us.        3599    IN    A    52.23.134.86
    
    
    ;; Query time: 45 msec
    ;; SERVER: 8.8.8.8#53(8.8.8.8)
    ;; WHEN: Wed Apr 18 23:35:59 CEST 2018
    ;; MSG SIZE  rcvd: 55
    Doing a recursive lookup might be somewhat slower for the first time, but once the answer is cached locally, lookups on my caching DNS server are much faster:

    Code:
    $ dig tp-link.us @192.168.1.10
    ; <<>> DiG 9.9.5-9+deb8u15-Debian <<>> tp-link.us @192.168.1.10
    ;; global options: +cmd
    ;; Got answer:
    ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 16426
    ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 13, ADDITIONAL: 1
    
    
    ;; OPT PSEUDOSECTION:
    ; EDNS: version: 0, flags:; udp: 4096
    ;; QUESTION SECTION:
    ;tp-link.us.            IN    A
    
    
    ;; ANSWER SECTION:
    tp-link.us.        3590    IN    A    52.23.134.86
    
    
    ;; AUTHORITY SECTION:
    .            496737    IN    NS    h.root-servers.net.
    .            496737    IN    NS    g.root-servers.net.
    .            496737    IN    NS    k.root-servers.net.
    .            496737    IN    NS    i.root-servers.net.
    .            496737    IN    NS    e.root-servers.net.
    .            496737    IN    NS    l.root-servers.net.
    .            496737    IN    NS    a.root-servers.net.
    .            496737    IN    NS    d.root-servers.net.
    .            496737    IN    NS    m.root-servers.net.
    .            496737    IN    NS    f.root-servers.net.
    .            496737    IN    NS    j.root-servers.net.
    .            496737    IN    NS    c.root-servers.net.
    .            496737    IN    NS    b.root-servers.net.
    
    
    ;; Query time: 0 msec
    ;; SERVER: 192.168.1.10#53(192.168.1.10)
    ;; WHEN: Wed Apr 18 23:36:23 CEST 2018
    ;; MSG SIZE  rcvd: 266
    Therefore, all devices in my subnet use two caching proxy servers in my local network, which in turn use the forwarders of my ISP. In addition, queries are forwarded to public DNS such as Google's DNS if the ISP's DNS should fail for whatever reason.

    BTW, you need to set up DNS on CPEs only for two reasons:

    - If you want to use domain names rather than IPs to define NTP servers to use for time synchronization

    - or if your CPEs provide DHCP services and need to communicate the DNS server's IP to be used to the DHCP clients.

    In the former case, it's more efficient to also set up a local NTP service and use IPs on CPEs (or fast-resolving local DNS names). But if you use the ntp.org pool of time-sync servers, the ntp.org community asks you to only use domain names, because they use DNS for load-balancing queries.

    In the latter case, a CPE providing DHCP service is in most cases configured to act as a router, not as a dumb AP, albeit it's possible to even use DHCP on APs in addition to DHCP on the router for high availability or load-balancing (but then ensure to separate the DHCP's IP pools carefully).
    Last edited by R1D2; 04-18-2018 at 22:01.


 

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