12 replies to this topic

[thelaststop]

Hey all,

Just looking over the different classes of IP addresses and was wondering how one would be able to tell which class an IP address belonged to just by looking at it. This question came up on the practice exam and I got it wrong.

Thanks!
Jeff

[NickHeel]

Class A: 1.0.0.1 to 126.255.255.254; Supports 16 million hosts on each of 127 networks.
Class B: 128.1.0.1 to 191.255.255.254; Supports 65,000 hosts on each of 16,000 networks.
Class C: 192.0.1.1 to 223.255.254.254; Supports 254 hosts on each of 2 million networks.
Class D: 224.0.0.0 to 239.255.255.255; Reserved for multicast groups.
Class E: 240.0.0.0 to 254.255.255.254; Reserved.

Ranges 127.x.x.x are reserved for loopback tests, for example, 127.0.0.1. Ranges 255.255.255.255 are used to broadcast to all hosts on the local network.

[dbough]

Exceptions to the rule:
These are private IPs - they cannot be assigned by a RIR

10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255

These were implemented because we're just plain running out of new IP addresses (in the IPv4 scheme anyhow.)

They should all be considered class C and carry a subnet of 255.255.255.0

[laldrich]

Excellent posts, all!

[thelaststop]

Awesome! Thanks to all. I didn't find the range of IP addresses in either of the books I was using, just the reserved set of IP addresses.

[James]

The Class-Octet Table
Class	First Octet	Example	Default Subnet	Typical Application
A (netid . hostid . hostid . hostid)	1-126	17.14.22.211	255.0.0.0	University Network System
B (netid. netid. hostid. hostid)	128-191	143.144.1.1	255.255.0.0	Corporate System or Hospital Network
C (netid. netid. netid. hostid)	192-223	204.213.288.222	255.255.255.0	Small Business, Home Internet Connection

[bas]

So what if my girlfriend is on a 142.24.20.0 /31 but im a subnet 0?
Can we still summarize? Or at least make it a VLSM relationship.....

Just checking if my picture will show this time...haha

People who never laugh and take everything serious must frown a lot.

Greets from the low lands,

Bas

[luckyiyke]

hello nickfled or any one around,
plz i want u to remind me how you got those number of hosts and the networks eg. in the class A IP ads., you got 16 million hosts on the 127 networks.i have and idea but want you to strick this out for me.
thanks as u provide the solution for me
I LOVE THIS HOUSE

[Samasters]

I dont know if this is the right place to post this, maybe i should've created a new topic, but anyways.. I know that there are Class D, E and F ip addresses, what do these do? and like, how do you know if the ip addresses are of these types?

[karlwies]

Exceptions to the rule:
These are private IPs - they cannot be assigned by a RIR

10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255

These were implemented because we're just plain running out of new IP addresses (in the IPv4 scheme anyhow.)

They should all be considered class C and carry a subnet of 255.255.255.0

Your my new best friend.

[damien275x]

ok thanks very much for clarifying

[deepak.panwar]

ok thanks very much for clarifying

wt is concept of valid-subnet numbers?????

[fly351]

A neat trick to use:

Convert the first (leftmost) octet to binary. Now, where does the first zero occur? The first occurrence of a zero can determine what class this is. For example:

0110 0010 --> 1st Zero is in leftmost spot, class A
1001 1100 --> 1st Zero is in the spot after the first, class B
1101 0010 -->1st Zero in third spot, class C

wow thats awesome, thanks for that!!

Edited by fly351, 27 August 2008 - 10:02 AM.