Re:DNS servers that offer privacy and filtering
by johnchristopher on Wednesday February 06, 2019 @07:32AM
(#19094585)
So, what should we ping for testing Internet connectivity ?
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Re:DNS servers that offer privacy and filtering
by teddyh on Wednesday February 06, 2019 @07:38AM
(#19094614)
There’s ping.sunet.se as maintained by the Swedish University Network (i.e. the network connecting Swedish Universities; there is no single “Swedish University”).
Re:DNS servers that offer privacy and filtering
by snazz on Wednesday February 06, 2019 @07:44AM
(#19094652)
The advantage of pinging IPs is that you don’t have to have a working DNS setup to test your connection. If DNS does work, then your connection probably works, too.
Re:DNS servers that offer privacy and filtering
by 1_player on Wednesday February 06, 2019 @08:27AM
(#19094869)
In this case one should run "ping -n", otherwise ping will hang trying to resolve the IP into an hostname, if the DNS is misbehaving or not responding.
Re:DNS servers that offer privacy and filtering
by sathackr on Wednesday February 06, 2019 @11:05AM
(#19096237)
what default(included in OS) ping utility tries to reverse-lookup an address before pinging, and hangs if it can't.
I've never observed this in any version of Windows nor Linux.
Re:DNS servers that offer privacy and filtering
by tinus_hn on Wednesday February 06, 2019 @07:51AM
(#19094693)
You are better off using traceroute to one of these addresses, you should at least get some route outside of your own network.
Re:DNS servers that offer privacy and filtering
by bluejekyll on Wednesday February 06, 2019 @08:09AM
(#19094781)
Traceroute uses ICMP as well, and may send more packets then ping. It works by setting the TTL on the ICMP packet, which is the number of route hops to traverse before the packet is dropped. Routers are supposed to ( this can be disabled, and is why you get * * * sometimes) respond with a TTL expired. So it starts with a TTL of 1, and then increments by 1 after each hop is discovered (or no response in some timeout).
Re:DNS servers that offer privacy and filtering
by detaro on Wednesday February 06, 2019 @09:00AM
(#19095072)
On unixes, traceroute typically uses UDP by default (nowadays, ICMP is often an option, as are TCP SYN packets). Windows' tracert uses ICMP.
I believe this is because you need root privileges/special capabilities to send ICMP packets.
Re:DNS servers that offer privacy and filtering
by bluejekyll on Wednesday February 06, 2019 @09:32AM
(#19095296)
Yes. I wasn’t perfectly clear there. You’re correct for the initial src packet, the TTL exceeded response is ICMP, I think always.
Re:DNS servers that offer privacy and filtering
by tinus_hn on Wednesday February 06, 2019 @01:29PM
(#19098080)
The important difference is that you can trust no host on the internet to actually respond to pings, especially not machines prone to receive DOS attacks, like public DNS resolvers. Traceroute is for testing connectivity, ping is an archaic test to see if a machine is running.