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For as long as I can remember, I've always used the IP 4.2.2.2 when testing network connectivity using ping. What is significant about this IP, and when did this practice start?

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4.2.2.2 to 4.2.2.4 are public DNS servers, with really easy to remember IPs. –  Chris S Apr 15 '10 at 17:42
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I have never used this address even though I was aware of it. It always seemed like a bad idea to use abuse a public DNS server in this way. I wonder how much bandwidth per day is spend on simply responding to ICMP requests. I have seen this in scripts that run every minute to check that the internet is up. –  Zoredache Apr 15 '10 at 17:57
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Last I looked 2-3% of the bandwidth of the internet is being used (abused?) for ICMP traffic. The network professionals (router / long-haul optical) that I know don't do this. They ping, but usually to the point where their control ends. There has been / is talk of blocking ICMP traffic from outside of the peering points. –  dbasnett Apr 15 '10 at 18:22
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I tend to use 8.8.8.8 –  Tom O'Connor Apr 14 '11 at 15:52

5 Answers 5

up vote 20 down vote accepted

I ping it because it has always been up, and is easy to remember when DNS isn't working. But you might want to read this for more information: http://www.tummy.com/Community/Articles/famous-dns-server/.

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Interesting story, thanks for posting that. I never used it as a DNS server, but use it a lot to test for internet connectivity along with other IPs. Cannot rely on just one external IP for testing... –  xeon Apr 15 '10 at 17:48
    
+1 for easy to remember. When testing "why can't I get to this website", it's an IP that you know that you can get to so that you can test if it's the DNS that's wonky. –  Kevin M Apr 15 '10 at 17:53
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Makes sense that the source was BBN. –  gnavi Apr 15 '10 at 18:03

Via Dan Farrell (dannosite.com) @ http://www.tomshardware.com/forum/169983-46-what

I am going to take credit for 4.2.2.2 being used as a DNS server entry in your router... here's the story-

In 1998, I was managing a network operations center with a few support technicians. Early on in training these guys, I told them to ping 4.1.1.1 to see if the Internet was 'up', because 4.1.1.1 seemed like the "411" from phone calling... easy to remember when you were panicky (as they could become when our network had problems).

One day 4.1.1.1 stopped responding to pings, and we freaked out for a second- but only it was down. I immediately responded with, "Well, then what about 4.2.2.2?", just incrementing the 1's to 2's. It NEVER went down. It soon became our defacto test host to ping.

After a very short while, we were curious as to what this address was used for... and not being from the NE where it was originally used in the GTE network, we didn't already know it was a secondary caching-only resolver. But we soon found out... and also found that it was usable from outside GTE's network. So when we needed a quick DNS server to use ... we used 4.2.2.2.

I think it spread- not only as a DNS server to use, but also as a ping host test. I've definitely used it in my network administration career and told others to use it. But to hear it come back as a suggestion to me makes me smile.

Personally I think it's insecure that Level3 (which now controls it) allows it to continue to resolve for clients outside of it's network... but that doesn't stop me from using it

Dan Farrell dannosite.com

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beat me by seconds. Having said that, I've been in I.T. for over 15 years and this is the first I'd heard of pinging 4.2.2.2 –  GregD Apr 15 '10 at 17:44
    
I'm pretty sure I was pinging it before 1998 :-) –  gnavi Apr 15 '10 at 17:52
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Even though Dan Farrell takes credit for spreading it around, he certainly didn't register it and there is some question as to if he is really the source. We'll probably never know. Even the comment immediately after Dan's on the tomshardware link is disputing it. –  Jed Daniels Apr 15 '10 at 17:53
    
At one point in it's history, when I was trying to figure out what it was, 4.2.2.3 or .4 reverse-resolved to dont-steal-dns-service.gte.net (or something similar to that) –  Jason Apr 15 '10 at 19:17
    
That story sounds made up. Why would a manager of a NOC pick an IP at random (4.1.1.1) to use as their test of whether their NOC had connectivity? And secondly, after it failed and freaked him out why would he switch to another random IP (4.2.2.2)? –  ITGuy24 Apr 15 '10 at 20:44

If I have DNS resolution, I always ping Google.com since their DNS entries will send me to something near me that is responsive and it's extremely unlikely that it will be blocked. Even 4.2.2.2 stands a chance at being blocked if I walk into a client's office that had a hardcore admin who explicitly blocked some well known public services in the name of security or passive aggressive tendencies.

If I don't have DNS resolution, I tend to ping 208.67.222.222 or 208.67.220.220 (and hope there was no previously entrenched hardcore admin who blocked those at the gateway). Those are OpenDNS's two IP addresses. Not the easiest to remember, however they're worth remembering (since I use OpenDNS on everything that resolves internet names) so once you've memorized them it's a simple act of mind-muscle memory to type it.

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The problem with opendns is it will resolve unknown addresses to its own servers and send you to their BS search site. Very annoying if you're troubleshooting a DNS resolution issue. –  einstiien Apr 15 '10 at 19:06
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I tend to use google.com too. The 6to4 relay anycast address (192.88.99.1) would be a good candidate for a ping test, since it will be on your provider's network if they have a 6to4 relay, or at least nearby. –  Gerald Combs Apr 15 '10 at 20:21
    
@einstiien: Very true. That's how they make most of their cash. so I usually ditch using their servers on the particular client that I'm using to track down DNS issues. –  Wesley Apr 16 '10 at 0:27

Hey everybody... it's me, Dan. I'm the guy who made this claim, and I'm here to talk more about it. Here's the long, drawn-out version of what happened.

I was managing a NOC for a fixed-data wireless company in Florida at the time- fuzion (gofuzion.com - I could write a book about that place). I had a few guys working with me that were relatively new to the networking world. Heck, at that time, so was I, only having a few years of skin in the game.

Because of the novice-level skills brought to bear, I had guys who couldn't pull up a website on their own workstation and would freak out that the 'Internet was down'. Honestly, it was pretty pathetic. One kneejerk reaction everyone had was to ping yahoo.com. That's nice, but involves DNS resolution, so it's prone to failure. They, of course, couldn't remember the IP address to Yahoo, and Google wasn't up (to any real degree) at that point, so what was a simple IP address that everyone could remember that would be up and work reliably and consistently? Remember, this is many years ago, when carrier stability was a sales point, not a forgone conclusion.

I had, at that time, recently put together our WUG (version 3 I think, yay!) map together and wanted some outside hosts for checking. I wanted a pure-ip address that was easy to recognize as well. I putzed around and pinged simple addresses... 1.1.1.1, 2.2.2.2, and so on. I thought about a conversation I had with my boss earlier in the day (a truly gifted man by the name of Robert Campbell), who related back the resiliency of the PSTN. It hit me... telephone service had 411 for information. 4.1.1.1 ... just one more digit and boom goes the dynamite... and it PINGS!. I put it in my WUG map and forgot about it for a week or two.

I go back to review my map and this host has never gone down. I was too lazy previously to see who it belonged to, but now my curiosity was piqued. How stupid did I feel? It was a DNS server for GTE. Of course it was bound to be up most of the time. Back on the floor of the NOC, guys were still being dumb (this, for some, never changed. I'm sure all here can relate. We had a term for them pulled from the Denver office... "tits on a bull". But I digress.) They'd freak out when they or a client would have connectivity problems... and from there I told them, "Ping 4.1.1.1 . It will always work if your connection to the general Internet works. It's like 411 for the Internet." I know, super-cheesy. But I learned that super-cheese worked in tense situations, not just with nachos.

It worked. Guys stopped trying to ping DNS names or remembering their home cable/dsl address that would likely change anyway. They could just remember this simple address.

One day, I suppose they turned off ICMP- it stopped working. Guys in the NOC weren't crying, but they definitely had their panties in a twist. "4.2.2.2" was given in frustration by moi, which also coincidentally was the secondary to 4.1.1.1 (I think, could be wrong), and was responding to ICMP. It stuck. It spread. That's how it goes sometimes.

On the phone I heard these guys telling clients to ping 4.2.2.2 to test connectivity. I heard them on the phone with vendors testing with the address. What made me smile one day a couple years later was a frantic front-line DSL phone tech walking me through my home connectivity outage. "Ping 4.2.2.2" she quipped. Did I feel a little warm inside? You betcha.

So that's it. Did I invent it? For me in my little world, yes. Could someone else have already (or somewhat simultaneously) done it, like the radio or flight or any other actually important thing that has some actual impact in our lives? I hope this puts an end to the rumors. (reposted on mywebsite)

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Hi Dan, welcome to Server Fault. You should set up an account and stick around. :) –  Doug Luxem Apr 14 '11 at 13:48

I generally use 8.8.8.8 which is a public google dns server, even better to remember but not as old as 4.2.2.2, details HERE

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