Linux - NetworkingThis forum is for any issue related to networks or networking.
Routing, network cards, OSI, etc. Anything is fair game.
Welcome to LinuxQuestions.org, a friendly and active Linux Community.
You are currently viewing LQ as a guest. By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features. Registration is quick, simple and absolutely free. Join our community today!
Note that registered members see fewer ads, and ContentLink is completely disabled once you log in.
If you have any problems with the registration process or your account login, please contact us. If you need to reset your password, click here.
Having a problem logging in? Please visit this page to clear all LQ-related cookies.
SDN 101: An Introduction to Software Defined Networking
Discover the advantages of SDN.
SDN has quickly become one of the hottest trends in IT. But not all SDN solutions offer real software-defined functionality. As more enterprises consider SDN, they want to know, “What is SDN? And what are the real benefits?” If you're ready to explore the advantages of SDN, and want to know how it should be implemented within your enterprise, start by reading our introductory white paper.
Click Here to receive this Complete Guide absolutely free.
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?
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.
Distribution: OpenBSD 4.6, OS X 10.6.2, CentOS 4 & 5
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.
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?