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Old 05-01-2012, 05:07 PM
green
 
Default ping: slow with low latency?

I have a strange networking problem. There is something wrong between my
host (Debian wheezy) and a VPS (Debian squeeze). Everything has been working
great until approximately yesterday; now ssh connections only work for a
short time. I have reduced to minimal firewalls on both systems, and another
host on the same local network works fine. The most obvious symptom is this
(domains and IPs redacted):


$ time ping -c1 vps-fqdn
PING vps-fqdn (64.n.n.n) 56(84) bytes of data.
64 bytes from 64.n.n.n: icmp_req=1 ttl=43 time=60.1 ms

--- vps-fqdn ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 60.156/60.156/60.156/0.000 ms

real 0m5.145s
user 0m0.000s
sys 0m0.000s


Why does it take 5 seconds to receive a 60 ms ping reply? Also, if I hit ^C
quickly:


time ping -c1 vps-fqdn
PING vps-fqdn (64.n.n.n) 56(84) bytes of data.
^C64 bytes from 64.n.n.n: icmp_req=1 ttl=43 time=51.6 ms

--- vps-fqdn ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 51.611/51.611/51.611/0.000 ms

real 0m0.300s
user 0m0.000s
sys 0m0.000s


Why does ping not display the ping-reply immediately and exit?

Thanks
 
Old 05-01-2012, 06:16 PM
Pascal Hambourg
 
Default ping: slow with low latency?

Hello,

green a écrit :
>
> $ time ping -c1 vps-fqdn
> PING vps-fqdn (64.n.n.n) 56(84) bytes of data.
> 64 bytes from 64.n.n.n: icmp_req=1 ttl=43 time=60.1 ms
>
> --- vps-fqdn ping statistics ---
> 1 packets transmitted, 1 received, 0% packet loss, time 0ms
> rtt min/avg/max/mdev = 60.156/60.156/60.156/0.000 ms
>
> real 0m5.145s
> user 0m0.000s
> sys 0m0.000s
>
>
> Why does it take 5 seconds to receive a 60 ms ping reply?

Probably because of the reverse DNS resolution which timed-out.
Try ping -n to avoid reverse DNS resolution.
Also try to reverse resolve 64.n.n.n with {dig,host,nslookup} and see
what happens.


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