"Google unicast public DNS servers" s/unicast/anycast/, I keep forgetting that term.
On 22 March 2015 at 22:28, Amos Shapira <amos.shap...@gmail.com> wrote: > 1. Sounds like the ip's in your resolv.conf are wrong. Where does the > server get them from? ip's 8.8.8.8 and 8.8.4.4 are the Google unicast > public DNS servers. They are reliable but it's not optimal for a server to > have to reach out to them on every query. > > 2. The ssh login is possibly slow because the ssh server is configured to > try to reverse-resolve the incoming client ip address for logging. Look for > "UseDNS" in your SERVER config (/etc/sshd_config). The default is usually > "no" but perhaps in your case it's on. > > 3. Telnet is not a good indicator of reachability of DNS servers, DNS is > UDP based and usually even the TCP port 53 is blocked because no one is > supposed to have to access it. On the other hand, traceroute (yes, good old > traceroute, as opposed to ping and tcptraceroute) uses UDP packets and you > can tell it to use port 53 as destination so perhaps try that (again - pass > "-n" flag to it to stop it from failing to reverse-resolve the ip address > of each response). > > Good luck. > > On 22 March 2015 at 22:13, Gabor Szabo <ga...@szabgab.com> wrote: > >> I tried that, and although I am not sure what should I look for in there >> it seems to be claiming >> >> rt_sigsuspend([];; connection timed out; no servers could be reached >> >> >> I tried to telnet 72.14.179.5 53 (one of the DNS servers) and that did >> not got a response. >> >> >> Anyway, Linode support told me to add this to the resolve.conf >> >> nameserver 8.8.8.8 >> >> nameserver 8.8.4.4 >> >> and that seemed to do the trick. >> >> Gabor >> >> On Sun, Mar 22, 2015 at 1:00 PM, guy keren <guy.choo.ke...@gmail.com> >> wrote: >> >>> >>> run this on the host: >>> >>> strace host www.google.com >>> >>> and scan the output. >>> >>> more efficient then guessing. >>> >>> --guy >>> >>> On 03/22/2015 12:50 PM, Gabor Szabo wrote: >>> >>>> Hi, >>>> >>>> I run an Ubuntu based VPS on Linode. >>>> I few hours ago the machine stopped resolving hostnames. >>>> I think it was after an "aptitude safe-upgrade" and a reboot, but I am >>>> not sure. Maybe was like this earlier. >>>> >>>> It takes ages to ssh to it, once I got to the machine I can ping IP >>>> addresses from it, but I cannot ping anything with a hostname. >>>> >>>> this is what I have in resolv.conf >>>> >>>> # cat /etc/resolv.conf >>>> >>>> domain members.linode.com <http://members.linode.com> >>>> >>>> search members.linode.com <http://members.linode.com> >>>> >>>> nameserver 72.14.179.5 >>>> >>>> nameserver 72.14.188.5 >>>> >>>> options rotate >>>> >>>> >>>> I tried to replace the nameservers with others that are listed in >>>> another of my servers, but that did not make a change. >>>> >>>> How can I track down what has the server stopped resolving hostnames? >>>> >>>> Accessing the server via HTTP work as expected. >>>> >>>> Gabor >>>> >>>> >>>> >> _______________________________________________ >> Linux-il mailing list >> Linux-il@cs.huji.ac.il >> http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il >> >> > > > -- > <http://au.linkedin.com/in/gliderflyer> > -- <http://au.linkedin.com/in/gliderflyer>
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