Difference between IP address and DNS?

SurferdudeHB

What's the difference when pinging/ pointing using the IP address or DNS?

RTmarc

Do you understand the relationship between an IP address and DNS?

tiersten

Not sure what exactly you're asking. Are you asking what the point of DNS is? Or what the difference between using an IP address and a DNS name is?

DNS.

SurferdudeHB

I understand that DNS is the translation of an IP address into a alias name.

So for example, what's the difference when you type in Yahoo! instead of http://10.163.3.14

Slowhand

SurferdudeHB wrote: »

I understand that DNS is the translation of an IP address into a alias name.

So for example, what's the difference when you type in Yahoo! instead of http://10.163.3.14

For a human, it doesn't make a bit of difference. The DNS name is there to help you remember what it is, since names are easier to remember than numbers. However, there are DNS-enabled applications and processes that need to know DNS names, relying on a DNS server to translate that name into an IP address, since that's how those particular apps were designed. However, just going to a browser and typing in ping cnn.com, versus typing ping 157.166.224.25. . . nada, zippo, no difference at all. Well, unless your DNS service isn't working, then the DNS name won't work.

Forsaken_GA

DNS has more of an effect than you might think. When weird things start popping up, I've learned the hard way that the first thing to check is DNS. The real culprits are the reverse-DNS lookups.

As an example -

Recently we had our DNS servers go offline for a period of 10 minutes or so while a load balancer had to be rebooted. That cascaded into some seriously weird errors, the weirdest of which were mysql related.

The mysql server was accepting connections over a private backend, with private IP addresses. Absolutely nothing touchable, absolutely nothing being routed, just a bunch of servers with their second NIC's plugged into a common switch.

The mysql server was stalling and piling up connections, and as a result, all of the servers that depending on pulling data from mysql were unusable.

The problem? mysql does reverse dns lookups on all IP's by default. So when it sees a connection for 10.10.100.43, it still tries to do a reverse, and in the normal course of things, that returns nothing... but it returns it *immediately*, so the connection process moves on. If the DNS server(s) that are configured to be queried aren't available, then the reverse query is stuck in limbo waiting for the lookup attempt to fail, which causes things to backup, and other things to timeout, and so on and so forth.

captobvious

SurferdudeHB wrote: »

I understand that DNS is the translation of an IP address into a alias name.

So for example, what's the difference when you type in Yahoo! instead of http://10.163.3.14

Shouldn't this be in the A+ forum?

SurferdudeHB

captobvious wrote: »

Shouldn't this be in the A+ forum?

Na.. I'm studying for the CCENT so this is my home

Met44

So for example, what's the difference when you type in Yahoo! instead of http://10.163.3.14

When you type "Yahoo.com" into a browser's address bar and press Enter, your computer sends out a DNS request to the DNS server you have configured in your IP settings to ask what the IP address of "Yahoo.com" is. After the reply comes back, your computer uses the IP address contained in the DNS response to establish a connection with "www.yahoo.com".

If you provided an IP address instead, then no DNS lookup would be attempted. Your computer would simply attempt to initiate a TCP session with whatever IP address you provided.

The difference is the DNS lookup.

BroadcastStorm

IP address - 1.1.1.1
netbios - one
FQDN - one.two.com

on windows OS there is lmhosts and hosts file, do a google and start reading about it, this are the basic form.

Forsaken_GA

Met44 wrote: »

If you provided an IP address instead, then no DNS lookup would be attempted.

Be very careful with statements like that. A very large amount of software does indeed do a dns lookup when given an IP, they just don't do a forward dns lookup. Even IP's are subject to dns queries.

Met44

If you provided an IP address instead, then no DNS lookup would be attempted.

Be very careful with statements like that. A very large amount of software does indeed do a dns lookup when given an IP, they just don't do a forward dns lookup. Even IP's are subject to dns queries.

A good point, but in the example that statement was extracted from, the browser will not attempt a reverse lookup for www.yahoo.com.

captobvious

SurferdudeHB wrote:

I understand that DNS is the translation of an IP address into a alias name.

So for example, what's the difference when you type in Yahoo! instead of http://10.163.3.14

captobvious wrote: »

Shouldn't this be in the A+ forum?

Sorry, I meant on the Network+ forum. This is basic networking stuff.