Ping default timeout setting

Ole Juul · 02-10-2009, 11:37 PM

I am running Kubuntu 6.04 and I've been using ping without setting any switches. When the host is down then it returns "unknown host". According to the man page the -W (timeout) option can be set, but there is no mention of what the default setting is. Can someone please enlighten me?

paulsm4 · 02-11-2009, 12:38 AM

Hi -

It's entirely implementation dependent.

I believe the default value for most versions of Linux is 10 seconds.

'Hope that helps .. PSM

j-osh · 02-11-2009, 12:50 AM

For iputils 2007-11-27 it seems to be 10 seconds at least it is the value it is initialized to. I am not sure if it scales that as packets are successfully received or not.

The man page give:
-W timeout
Time to wait for a response, in seconds. The option affects only timeout in absence of any responses, otherwise ping waits for two RTTs.

You can get the source code yourself from iputils if you wanted to dig into it.

Ole Juul · 02-11-2009, 01:22 AM

Thankyou for responding paulsm4 and j-osh.

It seems that if I ping my ISP then it goes on forever if I don't stop it. However if there is no response then it goes for a minute or more. That is the time I was interested in right now.

I just pinged a non existant url and it quit after about 5 seconds. Trying it the second time it quit right away. So, yes, there is some scaling factor relating to things beyond my emediate control.

Perhaps I'm not asking the right question since the DNS servers are obviously involved in the time that I'm looking for. I didn't realize that the situation was more complicated.

I'll try an old fashioned stop watch next time it happens.

archtoad6 · 02-18-2009, 06:48 AM

Minor point: Are you sure it's "Kubuntu 6.04" not "Kubuntu 6.06" like the rest of 'buntu Dapper?

Ole Juul · 02-20-2009, 10:05 PM

Quote:

Originally Posted by archtoad6

Minor point: Are you sure it's "Kubuntu 6.04" not "Kubuntu 6.06" like the rest of 'buntu Dapper?

Perhaps not so minor.

Code:

$ uname -a
Linux SCO 2.6.15-53-386 #1 PREEMPT Mon Nov 24 17:50:35 UTC 2008 i686 GNU/Linux
$ cat /etc/issue
Ubuntu 6.06.2 LTS \n \l

So yes, you're right.

chort · 02-20-2009, 11:17 PM

Quote:

Originally Posted by Ole Juul

I just pinged a non existant[sic] url and it quit after about 5 seconds. Trying it the second time it quit right away. So, yes, there is some scaling factor relating to things beyond my emediate[sic] control.

First off, you cannot ping Uniform Resource Locators as they contain extra meta information that is not contained in DNS. What you meant to say was "hostname".

Second, if a hostname cannot be resolved to an IP address, there's no IP to send a packet to, hence one cannot be sent. This is entirely different than trying to ping an IP address that cannot be reached by ICMP messages.

Most DNS caches these days have "negative caching", which is to say they not only remember recent hostname -> IP mappings that they've looked up, but they also remember when they couldn't find an IP for a particular hostname.

Ole Juul · 02-21-2009, 04:35 AM

Thank you for the clarification and information chort. (And the spelling/typo corrections too

.) That all makes sense.

I still don't know what the default timeout is for my particular Linux installation's ping executable. Generally I use the one that comes with WATTCP (presumably by Engelke) and it only does one ping by default and spaces multiple pings one second apart - limited perhaps, but friendly. Linux is less accessible and sparsely documented so I have to ask other people about many things.

Being an amateur (and beginner), the incomplete man page for ping is almost useless to me. It is both generic and unfinished. Can someone point me to some practical documentaion for this command as it is compiled into Ubuntu?