Topic: How to remove a DNS entry?

[Jason Judge]

I'm having a bit of trouble with a domain: mail.uk2.net.

My SME v5 is reporting this as 213.239.57.30 but it should be 213.239.57.89. Doing a traceroute from my server confirms a long string of servers to the wrong one (which has a reverse DNS of mailme.uk2net.com). Unless I am missing something here (I'm sure I am), I don't see how a traceroute can get me any further than confirming something ain't working right.

Now how can I tell where the problem is? Is cached on my SME server? If so, how do I tell my SME server to discard whatever IP it has for this domain and read it from my ISP again?

I suspect the problem is with the ISP - but equally would not put it past uk2 to have misconfigured a server somewhere (their mail servers are up and down like yoyos at the best of times).

I've tried searching the web for help, but nothing I can think of searching on comes up with anything useful. Any help would be appreciated - ruling out the SME server as the source of the problem is the first step.


-- Jason

[Patrick Hickey]

First thing is determine from WHERE your SME is receivng the bad DNS information. What DNS server do you point at? Did you define one in the config or are you using the default (hidden) DNS server entries which are generically provided by the software? If you defined one, ping the person in charge and put the onus upon THEM to flush it out. If you are using the generic DNS server list then....

The reverse DNS lookup is a great way to flush out errors. Use nslookup at the command prompt on the e-smith. Errors are not unique to your ISP or the folks you reference. Typos happen all over the net, all of the time and result in weird issues.

You might try a WHOIS searc to determine what master DNS server "serves" the apparently misconfigured server and then contact the hostmaster of that domain or ISP, etc. Include a text file with your nslookups and clearly depict what you think is the issue. They generally appreciate the data and make the fixes quickly.

To flush your internal DNS data you can just reboot, unless you wish to kill and restart the DSN daemon instead. There are defined intervals used by the DNS server and theough they are configurable, e-smith des not make them available in the GUI.

Do a Google on these words in relation to DNS and it'll make more sense....

Expire, Minimum, Refresh, Retry

regards,

patrick

[Jason Judge]

Thanks Patrick - that explained a lot. I didn't realise there was so much capability in nslookup.

The problem appears to have cleared itself up now. The IP addresses for the uk2.net mail servers took around four days to propagate around the World, and the order in which it propagated did not make it easy to follow. Pinging from Edinburgh, London, Paris and the US gave the correct IP address, while Manchester (UK), Hong Kong and Madrid and my Newscastle (UK) ISP gave the older incorrect IP address.

They (UK2) say it just took a long time to propagate, but I suspect one rogue DNS was busy reseting the IP back to the old address as fast as the new IP was being propagated by the main DNSs. It's just a hunch - but I got the 'incorrect IP' error message for periods of a few hours at a time - then nothing for a few more hours, then the error again.

This wasn't really an SME problem, but at least I know now that a reboot will prove this. As for tracing the real culprit and putting the onus on them - it seems it needs a lot of DNS knowledge and experience to do that.

Thanks,

Jason