One of my friend asked me an interesting question about relating IPv4 with IPv6. His question was: in dual stack setup, if we have IPv4 of a router/host, how can we find IPv6 associated with it?
Well, as far as I know there’s no direct way to relate IPv4 with IPv6 but there’s a nice trick out. Say e.g we have Google Public DNS operating at IPv4 - 8.8.8.8. To find IPv6 address of same server (if it exists at all), we can lookup for reverse DNS to get hostname, anurag@laptop:~$ dig -x 8.
Yesterday I called MTS Data Card support but their IVRS system was failing in giving me my balance details. Eventually I decided to email their support and glad to say support email was also easily available on their website.
Today I saw acknowledgement mail in spam. No big deal but I usually dig around genuine mails which go in spam to find exact cause. In this case I found mail was sent to me from customercare.
Yesterday I had a very interesting discussion with our senior administrator.
I was configuring reverse DNS records for our /24 block and I decided to use format - IP.static.domain.com thus if for IP 1.2.3.4, I pointed reverse DNS (PTR) to 1.2.3.4.static.domain.com
When I got chance to show my work to my senior administrator, he said - It’s wrong to use 1.2.3.4.static.domain.com in a hostname. Too many dots will make DNS resolution very slow (forward - reverse - again forward).
Which DNS resolver is better - ISP’s (default) DNS resolver, or Google Public DNS or the pioneer of DNS openDNS or even a local DNS server?
Let’s try to find out! I am sitting on a BSNL data link, and I will try to perform few tests to find that out: Available DNS resolvers to me:
BSNL DNS resolvers - 218.248.255.194 & 218.248.255.196 Google Public DNS - 8.8.8.8 & 8.8.4.4 OpenDNS - 208.
Few days back I visited Official Google Apps forum (one of my favorite places) and answered many questions. It was quite after some time i was there and found few cases/questions/problems as really interesting. Here’s one of the questions asked there by a admin named aol985 about SPF records.
His question:
As described in http://www.google.com/support/a/bin/answer.py?hl=en&answer=33786 , I set SPF record for mashfilm.ru domain to “v=spf1 include:aspmx.googlemail.com ~all”. But aspmx.googlemail.com currently does not resolves.