Thursday, November 23, 2017

Broken DNS


This seems to be the trend now a days in Corporate IT. Is it just Windows related? I don't know. It used to be that you could rely on DNS. Now you can't. Case in point - people hear talk about a machine known as "seacase". Others use the name usseacase. Whicih is correct? Well an educated guess would be they are one in the same and a DNS alias exists between them. IOW seacase is just a "pretty" name for usseacase.

Now I used to be that you could verify that with DNS, in particular you could use nslookup to find each of the names and see they have the same IP address. But more and more, Corporate IT DNS stuff is screwed up, perhaps in the name of security, such that they don't always resolve:

$ nslookup usseacase Non-authoritative answer: Server: <dns server> Address: 13.230.100.200Name: usseacase.<domain>.com
Address: 13.230.100.74


So we can look that one up but we can't lookup the other:

$ nslookup seacase *** <dns server> can't find seacase: Non-existent domain Server: <dns server> Address: 13.230.100.200

However ping works! And verifies that this is the same machine. So why doesn't DNS know about this?

$ ping seacase PING seacase (13.230.100.74): 56 data bytes 64 bytes from 13.230.100.74: icmp_seq=0 ttl=127 time=230 ms 64 bytes from 13.230.100.74: icmp_seq=1 ttl=127 time=0 ms----seacase PING Statistics----
2 packets transmitted, 2 packets received, 0.0% packet loss
round-trip (ms) min/avg/max/med = 0/115/230/115


Another pet peave of mine is people using either IP addresses instead of names (Do you refer to your friends by their cell phone numbers?) or using fully qualified machine names all the time when you don't need to...

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