169.254.0.1 - 169.254.255.254

[rookie1010]

Hi
in windows xp, automatic IP configuration results in random allocation of IP address between
169.254.0.1 - 169.254.255.254

are these addresses meant for homenetworking. how is this issue dealt with by routers. i mean if it is for homenetworking, then how do two LANs where windows xp has set these addresses up communicate with each other, i mean how are packets routed between them, since to my understanding, the router between them would have a conflicting routing table!

 

[Inaris]

In XP, if it senses a connection without recieving a DHCP address, it assigns it's self an address in the space given. This is a non routable address, simular to 192.168.2.1, meaning that outside the lan, it's no good. you need a router in place before it so you have a real address to go through.
I think the idea behind this was so that incase the DHCP server goes down, you can still get onto a machine even in a class B address space. but I don't know for sure.
The main concept was to make home netowrking easy without needing to know much about IP addressing, but I don't hink it's being used for much of anything. In a test lab setup, we used it to simplify addressing, but it was only temporary.
help any?

 

[rookie1010]

thanks for clearing up another of my concepts/micsonceptions.

why do we have three classes of addresses. you spoke about "even in a class B", does that mean class B is exclusive.

can you have home network address space in class A & D as well?

I was also wondering why, the need of an IP address in a home network scenario, since no routing is required, why can't the machines communicate on the basis of their MAC addresses only.

my understanding was that the network address is kind of @ while the MAC address is the true address.

 

[Inaris]

The mac is just a way to uniquly identify the machine on the hardware level. it's used more or less by the router to distiguish clients requesting addresses from the DHCP server.
IP is a simple and easy way to send information around, and can be segmented out into grouping without listing out all of the macs that are used. It's also an easier way then say having to put in all 2000 mac addresses into a list so you know what machines are yours and which are not. The classes designate the total number of IP's that can be used. Class A are 192.x.x.x Class B are 192.168.x.x class c are 192.168.1.x replace the 192.168... with what ever.
Since most medium sixed companies have several thousand a class B address is used to supply enough address space for the computers.
Class B are also the most common, for that reason.

does that help.

 

[TheMajor]

My uncle has exactly the same MAC as I do...how is this possible?

 

[Inaris]

unless it's been cloned it's not supposed to be possible. at least as far as I know, anyway... I'm going to look into that.
damn my curiosity!

EDIT-
Yup, as I thought, MAC's are Unique to each network device. if for some reason, you, or someone is cloning out a different mac, then you can do that, but for what reason, I don't know. The MAC is required for Layer2 communication in the OSI model.

just to expand a bit from the previous post, MACs are used at the data link level of the OSI model and IP's are used at layer 3, the networking level. Basically, a MAC sticks with the hardware, and an IP can change as needed.

 

[rookie1010]

any address with 192 as the first byte is a class C address
Class A addresses run from 1 to 126
and
class B from 128 to 191 according to understanding.

on a LAN which is not attached to the outside world through a gateway. the machines interact with each other using the MAC addresses with the following frame rough format(ethernet)

preamble:source MAC address:destination MAC address:IP header:data:CRC

since the MAC addresses are being used for identifiacation, what is the use of the IP Addresses?

 

[Inaris]

ok, here is it in all it's glory. It describes this in every detail.
http://www.bergen.org/ATC/Course/InfoTech/Coolip/

I was simply using a number for representation. not the actual class relationship.
Here is the decimal subdivision for the actual classes.
http://www.ralphb.net/IPSubnet/ipaddr.html

but i was wrong that the construct. Thank you for pointing that out...
more will follow...

 

[rookie1010]

thanks for all the info inaris

 

[rookie1010]

hey dude,
do you know any good sites on IGP protocols?
which start of with the basics with lots of illustrations!