Dns

Seems like k-root servers are having issue again. This is not the first time BSNL is having such issues. Last year I reported issue with K root server (which was actually because of downtime at Delhi node).  

Here’s some data for today’s case:

PING 193.0.14.129 (193.0.14.129) 56(84) bytes of data. 
64 bytes from 193.0.14.129: 
icmp_req=1 ttl=44 time=309 ms 
64 bytes from 193.0.14.129: icmp_req=2 ttl=44 time=312 ms 
64 bytes from 193.0.14.129: icmp_req=3 ttl=44 time=312 ms 
64 bytes from 193.0.14.129: icmp_req=4 ttl=44 time=312 ms 
64 bytes from 193.0.14.129: icmp_req=5 ttl=44 time=313 ms 
--- 193.0.14.129 ping statistics --- 
5 packets transmitted, 5 received, 0% packet loss, time 4001ms 
rtt min/avg/max/mdev = 309.687/312.019/313.333/1.289 ms  

 

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, 

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.del@mtsindia.in and the server which relayed this mail was:

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). And I should have used 1-2-3-4.static.domain.com

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:

1. BSNL DNS resolvers - 218.248.255.194 & 218.248.255.196
2. Google Public DNS - 8.8.8.8 & 8.8.4.4
3. OpenDNS - 208.67.222.222 & 208.67.220.220
4. Local DNS Server - BIND running on localhost - 127.0.0.1

Observing ping time:

BSNL DNS resolver:

--- 218.248.255.194 ping statistics ---

5 packets transmitted, 4 received, 20% packet loss, time 4001ms

rtt min/avg/max/mdev = 26.978/27.754/29.122/0.897 ms

--- 218.248.255.194 ping statistics ---
5 packets transmitted, 4 received, 20% packet loss, time 4001ms
rtt min/avg/max/mdev = 26.978/**27.754**/29.122/0.897 ms

Google Public DNS:

--- 8.8.8.8 ping statistics --- 5 packets transmitted, 
5 received, 0% packet loss, 
time 4001ms rtt min/avg/max/mdev = 121.147/121.878/122.951/0.783 ms

OpenDNS:

--- 208.67.222.222 ping statistics ---

5 packets transmitted, 5 received, 0% packet loss, time 4005ms

rtt min/avg/max/mdev = 217.678/**219.528**/222.034/1.717 ms

Next, localhost? :)