# The Structure of and IP Address / 32 bit address



## DreamSeller (Jul 10, 2009)

Learnt this at my todays IT courses and i thought it would be great to share with you guys


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## FordGT90Concept (Jul 10, 2009)

That's just binary -> decimal conversion.  It's the packet structure that is interesting.


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## Deleted member 3 (Jul 10, 2009)

Next he's gonna learn to calculate netmasks


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## hat (Jul 11, 2009)

What? 1=1? WHY WAS I NOT INFORMED OF THIS


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## Mussels (Jul 11, 2009)

i learned all that stuff and then forgot it... the theory was 100% useless when setting up networks, in practical use.


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## FordGT90Concept (Jul 11, 2009)

Mussels said:


> i learned all that stuff and then forgot it... the theory was 100% useless when setting up networks, in practical use.


Yup, just remember 192.168.0.1 or whatever.  It isn't hard to convert that to hex:
C0A80001

Or binary:
11000000101010000000000000000001


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## hat (Jul 11, 2009)

What is 192.168.0.1 used for?


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## Mussels (Jul 11, 2009)

hat said:


> What is 192.168.0.1 used for?



usually a router/DHCP server


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## FordGT90Concept (Jul 11, 2009)

Yup, that's the default router IP for D-Link routers.

The following are reserved for intranet use:
10.#.#.#
172.16.#.#
192.168.#.#

172.0.0.1 is reserved for loopback (aka localhost).


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## Deleted member 3 (Jul 11, 2009)

FordGT90Concept said:


> Yup, that's the default router IP for D-Link routers.
> 
> The following are reserved for intranet use:
> 10.#.#.#
> ...



And many other brands. Most routers have either 192.168.x.1, 192.168.x.100 or 192.168.x.254. Something in the 10.x.x.x is more rare, never seen the 172.16.x.x range used as default setting, not sure why.


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## Mussels (Jul 11, 2009)

DanTheBanjoman said:


> And many other brands. Most routers have either 192.168.x.1, 192.168.x.100 or 192.168.x.254. Something in the 10.x.x.x is more rare, never seen the 172.16.x.x range used as default setting, not sure why.



the 10.0.0.x range is very common here in australia, Telstra modems and routers all use it. (usually on really shit hardware too)


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## hat (Jul 11, 2009)

I've had only 2 routers and they were both 192.168.1.1

While we're talking about networking... what happens if you want more than 155 computers on a network (slots 192.168.x.100 - 192.168.x.255 are used up)


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## Mussels (Jul 11, 2009)

hat said:


> I've had only 2 routers and they were both 192.168.1.1
> 
> While we're talking about networking... what happens if you want more than 155 computers on a network?



you get 255, minus the router.

If you want more, you need to segregate into class C subnets, 192.168.0.1 for 254 users, 192.168.1.1 for the others. Set the subnet mask to 255.255.0.0 and communication will be possible between them, they merely need the gateway IP address set to the router and everything will be well.

where did starting at 100 come from? it starts at 1


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## FordGT90Concept (Jul 11, 2009)

DanTheBanjoman said:


> And many other brands. Most routers have either 192.168.x.1, 192.168.x.100 or 192.168.x.254. Something in the 10.x.x.x is more rare, never seen the 172.16.x.x range used as default setting, not sure why.


192.168.#.# is definitely the most common.  A Netgear I worked with for some reason thought 192.168.#.# was in use so it fell back to 10.#.#.# (99% sure it was faulty though).  I, too, have never seen 172.16.#.# but, it is reserved for intranet use by IANA.

Apparently, 192.168.#.# has 65k addresses, 172.16.#.# has a 1,000k addresses, and 10.#.#.# has 16,000k addresses.  I assume that, if 192.168.#.# isn't enough (consumer-class), they go straight to 10.#.#.# (enterprise-class) skipping the 172.16.#.# range.

http://en.wikipedia.org/wiki/Private_network


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## DreamSeller (Jul 11, 2009)

Mussels said:


> i learned all that stuff and then forgot it... the theory was 100% useless when setting up networks, in practical use.



very very true
im so noob at this fckn theory i wish we had the test in practice form


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## FordGT90Concept (Jul 11, 2009)

Mussels said:


> where did starting at 100 come from? it starts at 1


D-Link...
Device = 192.168.0.1
DHCP = 192.168.0.100-192.168.0.199

Netopia (aka Motorola)...
Device = 192.168.1.254
DHCP = don't use it 

But yeah, the router is almost always at 192.168.0.1 or 192.168.1.1


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## AltecV1 (Jul 11, 2009)

wow that is complicated


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