Hardware and IP Addresses...

[Caveman]

I assume the NIC stores the IP address on a computer? How about the MAC address? Please indicate if the following is true:

1) IP address is static and does not change (unless "forced" by some means)?

2) Mac address changes each time a connection is made to the internet?

Please help...

 

[Confused]

You've got it round the wrong way

MAC address is assigned to the network card itself. Some can be changed, but generally they are not.

IP addresses are (normally) dynamically assigned and are logical addresses, normally changing depending on your location (ie what network you are plugged into)


Confused

 

[WHipLAsh13]

Originally posted by: Confused
You've got it round the wrong way

MAC address is assigned to the network card itself. Some can be changed, but generally they are not.

IP addresses are (normally) dynamically assigned and are logical addresses, normally changing depending on your location (ie what network you are plugged into)


Confused

Confused has it the correct way.

 

[Caveman]

Based on what you said then, are the following statements true?

1) The MAC address on my NIC at home has an imprint of itself that my cable provider can "see" because my cable modem is routed into my NIC...

2) If I take my computer at home and plug the modem into another outlet from my provider the MAC will remain constant, but my IP will change...

3) At work (on a huge network), I have an IP address for my machine. Assuming I leave it plugged into the same port (and the IT folks don't do magic on their end), I should have the same IP address daya fter day after day, no matter how many times I reboot.

4) an IP address is not "coded" to any part of hardware (like a MAC), it's something the OS picks up and indicates to you when you ask for it...

Am I starting to understand correctly?

 

[Caveman]

Based on what you said then, are the following statements true?

1) The MAC address on my NIC at home has an imprint of itself that my cable provider can "see" because my cable modem is routed into my NIC...

2) If I take my computer at home and plug the modem into another outlet from my provider the MAC will remain constant, but my IP will change...

3) At work (on a huge network), I have an IP address for my machine. Assuming I leave it plugged into the same port (and the IT folks don't do magic on their end), I should have the same IP address daya fter day after day, no matter how many times I reboot.

4) an IP address is not "coded" to any part of hardware (like a MAC), it's something the OS picks up and indicates to you when you ask for it...

Am I starting to understand correctly?

 

[thorin]

Yup you've got it exactly backwards.

MAC is static and in most cases actually hardcoded (hardwired) into the device in question.

IP is not static and assigned via configuration (whether manual and long term or automatic and short(er) term).

Thorin

 

[Caveman]

So are the conclusions I draw in my second post valid? Thanks for your help...

 

[Confused]

To your next bits:

1) Often your cable modem is "linked" to a certain MAC address, which the cable provider can "see", via the modem (as such)

2) Yes, the MAC address will stay the same, but if you're using the same modem, and it's on the same cable (as all the outlets in your house are shared) you will have the same IP address. See 3.

3) Yes, you should, providing the computer is on, and the OS is keeping the "lease" updated. IP addresses have leases, an indicator of how long they are given to a computer. If the computer is on, then the computer will often request the same IP address once it's been given it. If however the computer is turned off when the lease runs out, and is not re-requested, then that address will be given to the next computer that asks for it. You will probably find that your computer at work could be moved to another network point, but as they will all be attached to the same physical network, with the same DHCP server (the thing that gives out IP addesses), AND providing the lease didn't run out, then you will have the same address.

4) Yes, that is right.


Confused

 

[WHipLAsh13]

Yep most are correct. Only one that could be incorrect is #3. Depending on how your network is setup this could be true or false. Most companies use a long lease time so this would be correct but some companies I have seen use very short lease times so you could technically get a different IP day to day.

 

[eLinux]

Originally posted by: Caveman
Based on what you said then, are the following statements true?

1) The MAC address on my NIC at home has an imprint of itself that my cable provider can "see" because my cable modem is routed into my NIC...

No. The cable modem itself has a MAC address, and that's all that the cable provider can see...

2) If I take my computer at home and plug the modem into another outlet from my provider the MAC will remain constant, but my IP will change...

MAC address is always constant. Period. The IP will probably not change. For you to understand this you have to realize that although DHCP assigns IP addresses dynamically, it generally gives you the same address if the addresses has not been reassigned and you still are within the lease period. This can be explained in a far more complex matter, but that's the general overview/idea.

3) At work (on a huge network), I have an IP address for my machine. Assuming I leave it plugged into the same port (and the IT folks don't do magic on their end), I should have the same IP address daya fter day after day, no matter how many times I reboot.

Not necessarily. I'm about 99.9999% sure, but the addresses will be reassigned if your lease period is over. Then again I'm not sure if it will reassign it if you are *actively* using a connection (sending frames and receiving them) and the lease expires.

4) an IP address is not "coded" to any part of hardware (like a MAC), it's something the OS picks up and indicates to you when you ask for it...

That is correct. IP addresses are *not* coded. You can have an IP address when you're at home using your cable, and if you pick the computer up and move it to your neighbors house, you'll get another one (assuming he is using DHCP, etc.)

Am I starting to understand correctly?

Sounds fairly accurate to me

 

[Caveman]

Thanks to all for your expertise! I'll be checking my IP now with regularity at work to see if I can track any expirations, etc... and learn more...

 

[hausdave]

Most windows networks will gave the same IP over and over to a given mac address even after expiration unless it is removed from active leases in the DHCP scope on the server (or device) that is providing DHCP for that network.

 

[WHipLAsh13]

Originally posted by: hausdave
Most windows networks will gave the same IP over and over to a given mac address even after expiration unless it is removed from active leases in the DHCP scope on the server (or device) that is providing DHCP for that network.

Which can happen quite often for networks with wireless devices or in public areas such as colleges. So it really can vary depending on the network setup